HQR15-01

Japan Geoscience Union Meeting 2016

The embodiment of the consecutive penetration tests in the Liquefaction-Fluidization place*Hideto Kimura1
1.Toho Chisui Co.,Ltd.
2011 occurred on March 11, 2011 Tohoku-Pacific Ocean earthquake and liquefaction and liquidity
phenomenon of the formation by the largest aftershock (less liquid fluidization), Jinami phenomenon
has occurred. Liquid flow of the embankment, man-made strata was observed also in the inland as
well as coastal areas by this earthquake. Depending on the structure, because it was observed inmany cases it can be used again if the lift or the subsidence part or return horizontally, thisstudy area is located in the man-made strata distribution area that has received the liquid
fluidization damage building construction jack-up by the steel pipe pile construction as therestoration method of the object has been selected. While the support layer depth and N values
measured for thickness confirmation were required upon installation rather than the usual standard
penetration test to implement the N value measured every 1m, continuous penetration test to
implement the N value measured every 50cm it was adopted. This is a distribution in the depth
direction as viewed from the N value of liquid fluidized layer, by performing as much as possible
detailed observation of the sample taken without creating a non-core section, an intermediatesurvey and the positioning of the standard penetration test and all core boring, as long as isbrought close to the no attempt, is considered rare example unparalleled is in that could also be
confirmed up to now as the investigation of the time less than after the disaster in one month.
Survey method is a continuous penetration test of 10-15m was carried out in 1 point (a total of 6
points) of each building vicinity, previously implemented only up to 20m 1 point corresponding tothe on-site center, this each sample detailed sample observation carried out close-up on the spotof the point was carried out in the indoor (on Workstation). Results of the investigation,
geological structure based on the 20m hole geological observations were classified as follows. 1stlayer (N value of 4/32-9) crushed stone, concrete silt mingled with fine sand at a layer thicknessof 0.40-1.25m - estimated non-liquid fluidized layer of fine sand mingled with silt.2nd layer issand layer (N value of 0/20-12) many very fine grain sand water at a layer thickness of 2.20-4.95m- N value of 3 or less in the middle part and in particular the entire base portion in a liquid
fluidized layer of fine-grained sand (minimum 0/20) the admit.3rd layer is clay layer (N value 1-5)
estimated fluid fluidized layer of fine-grained sand mingled with silt of the lens-shaped
distribution at a layer thickness of 0.85m.4th layer is foreshore after the beach sediment layer (Nvalue of 4/32-50 or more) non-liquid fluidized layer of fine-grained sand to the development of theblack beam at a layer thickness of 1.90-7.40m.5th layer is nearshore sediment layer (N value 14-50
or more) the confirmation layer thickness 13.60m bulk-free layer management in the array or silt
contamination of irregular sand particles (biological disturbance) and sand pipes and mud pipes andfine sand - silt mingled with fine-grained non-liquid fluidized layer of sand shells fine piece ismixed, of 5, which is a division. As advantages of the present survey methods, can also be appliedin the building bowling because it is a rule, a:N value measurement, there is a possibility thatcan discover the b:stratum fluidization trace (the discovery of re-liquefaction danger), on theother hand as the points to keep in mind, is a:hydrous very many samples need basket with shoe forfall prevention for easy to fall, focus on a flat break-all sand particles as much as possible thesample surface in the close-up of sample, sure unit investigation capable engineers in charge tothings like.

©2016. Japan Geoscience Union. All Right Reserved.

- HQR15-01 -HQR15-01

Japan Geoscience Union Meeting 2016

Keywords: Reliquefaction-Fluidization place, Advantage of continuous intrusive examination, Fault
of standard penetration test

©2016. Japan Geoscience Union. All Right Reserved.

- HQR15-01 -HQR15-02

Japan Geoscience Union Meeting 2016

Litho-stratigraphy on reclaimed land in northern Tokyo bay and liquefaction-fluidization
horizon at the 2011 off the Pacific coast of Tohoku Earthquake: from the geological survey
by continuous boring cores*Osamu Kazaoka1, Masaaki Uzawa2, Itaru Ogitsu1, Hisashi Yabusaki1, Atsushi Kagawa1, Takeshi Yoshida1, Akiko Kato1, Eri Honda1, Takashi Ogura1
1.Research Institute of Environmental Geology, Chiba, 2.Kanto Construction Co. Ltd.
Liquefaction-fluidization phenomena caused widely on reclaimed land along northern Tokyo bay at The
2011 off the Pacific coast of Tohoku Earthquake. Stratigraphy of this site is composed of the
middle- upper Pleistocene Shimousa group, the Holocene formation and Man-made formation inascending over. Shimousa group, under 41.7m depth, consists of mainly very dence sand bed with thinsilt bed and tephra beds. Holocene formation, from 41.7m depth to 5.53m depth, consists ofbioturbated soft silt beds, bioturbated very fine sand beds, coarse silt beds and fine –medium sandbeds with pebble from Kanto Loam formation. Man-made formation, over 5.53m depth, consists of cleanfine - medium sand beds, shelly coarse - very coarse sand bed, clayey fine silt bed and coarse silt
bed.
Primary sedimentary structure, lamination deformed or lost partially on sand bed in 2.65-3.75 and5.00-5.53m depth. It is presumed that these horizons were liquefied and fluidized on the 2011 off
the Pacific coast of Tohoku Earthquake.
Keywords: Liquefaction-fluidization, the 2011 off the Pacific coast of Tohoku Earthquake,
continuous boring core, Man-made strata, reclaimed land

©2016. Japan Geoscience Union. All Right Reserved.

- HQR15-02 -HQR15-03

Japan Geoscience Union Meeting 2016

Luminescence age of Holocene sand dunes and alluvial lowlands at costal area in Tonbetsu
plain, northern Hokkaido, Japan*Reisuke Kondo1, Kiyoyuki Shigeno2, Akihiro Yokota2, Sumiko Tsukamoto3, Shigetoshi Inui4, Yosuke
Miyairi5, Yusuke Yokoyama5, Hiroko Fujita6, Takato Takemura7, Chieko Takeshita8, Tatsuhiko Sakamoto8, Hiroshi Ushiro9
1.Kogakkan University, 2.Meiji Consultant co.,ltd. , 3.Leibniz Institute, 4.Hamatonbetsu Town,
Education Board, 5.University of Tokyo, 6.Hokkaido University, 7.Nihon University, 8.Mie
University, 9.Hokkaido Museum
In Tonbetsu plain, northern Hokkaido, a series of fluvial terraces and sand dunes are distributed
whose detailed chronology is unknown. Reconstructing the Holocene geological evolution in Tonbetsu
plain is very important, due to the existence of many prehistoric sites are found on the sand dunes
and their around area and also due to a rare ecosystem around the sand dunes and alluvial lowland(Fujita, 2014; Hamatonbetsu Town Education Board, 2014). To establish the chronology of young
coastal sediments and fluvial terraces in Tonbetsu plain we used a combination of different
luminescence dating methods including OSL dating of quartz and post-IR IRSL (pIRIR; Thomsen et al.,2008) dating of feldspar using both fine silt and sand sized grains. The OSL signal of the coarse
grain quartz samples from the dune sand is dominated by slow components, suggesting that the sandsized quartz is not a suitable dosimeter (Thiel et al., 2015). Therefore we applied pIRIR dating of
K-feldspar (pIR150; Reimann and Tsukamoto, 2012) to the sand samples.
The results indicate that, 1) pIR150 dating is an effective tool to date the Holocene sand sized
sediments in Tonbetsu plain, 2) it is possible that the sources of quartz are different dependingon grain size or geologic period, because the OSL ages of fine grain quartz are reliable in the
study area (Kondo et al., 2007), 3) the sand dunes have been formed from the inland side
sequentially after ca. 5.7 ka following maximum of the Holocene transgression in central Tonbetsu
plain, 4) in southeastern Tonbetsu plain, the sand dune formation has been continued until the late
Holocene, with alterations of stable (inactive) stages and destruction events by storm surge, and5) in northwestern Tonbetsu plain, the sand dune formation stopped by the late Holocene, or younger
sand dunes close to the coast were eroded completely by waves.
We will also show the luminescence dating results of the alluvial lowland and lower fluvial
terraces in the study area.
Reference
Fujita(2014) Hokkaido University Press, 272p.; Hamatonbetsu Town Education Board(2014) Hamatonbetsu
Town Education Board, 223p.; Kondo et al. (2007) Quaternary Geochronology, 2, 260-265.; Murray andWintle(2000)Radiation Measurements, 32, 57-73.; Reimann and Tsukamoto(2012) Quaternary
Geochronology 10, 180-187.; Thiel et al. (2015), Quaternary Geochronology, 29, 16-29.; Thomsen etal. (2008)Radiation Measurements, 43, 1474-1486.
Keywords: sand dune, alluvial lowland, pIRIR / OSL dating, Tonbetsu plain, Holocene©2016. Japan Geoscience Union. All Right Reserved.

- HQR15-03 -HQR15-04

Japan Geoscience Union Meeting 2016

Identification of Nantaisan Shichihon-sakura/Imaichi tephra (Nt-S/I) in the sediment core
MD01-2421 collected off the Kashima coast, Japan*Kaori Aoki1, Takehiko Suzuki2
1.Rissho University, 2.Tokyo Metropolitan University
IMAGES core MD01-2421 (45.83 m) from the northwest Pacific Ocean off central Japan yielded
twenty-three tephra beds. Descriptions of the twenty-three tephra beds have been made using the
major-element composition of glass shards and refractive indices (RI) of glass shards andphenocrysts. As a result, at least seven on-land maker tephra layers have been identified. Twotephras, AT and Aso-4 come from Kyushu: Aira and Aso calderas. Four tephras come from central
Honshu: Ag-KP from Mt. Akagi, Hk-TP from Hakone caldera, On-Pm1 from Mt. Ontake and Tt-D from Mt.
Tateyama. One tephra, TG as the lowest layer of all, comes from northeast Honshu and are correlatedaround the coastline of southern Fukushima. Later, we have been studying the source volcanoes ofremaining sixteen tephra beds. In this study, we report the new information on the source of Tephra
1 obtained recently.
Tephra 1 (925.6-933.1 cm) are characterized by coarse and bad selected volcanic sands consisting ofwhite to pale brown pumice and black scoria which grain size is limited to 3 mm. Its thickness is
7.5 cm disturbed in liquid mud. The deposited age of this tephra is estimated at 17.7±1.38 ka basedon the oxygen isotopic stratigraphy of the benthic foraminifera and the calendar ages offoraminiferal fossils calculated from the accelerator mass spectrometry (AMS) 14C ages. Pumices arecross-foaming and include many microlites. Refractive index of volcanic glass shards exhibits
bimodal as 1.498-1.503 and 503-1.509. Aoki et al. (2008) pointed out that 63-125 µm size particles
consist of weathering minerals besides volcanic materials and geochemistry of 125-250 µm size
volcanic glass shards indicated heterogeneity, hence there is a strong possibility that particles
limited to 250 µm in this tephra bed included contaminant besides essential volcanic materials.
To address this problem, we hand-picked 2-3mm size pumice grains, and crushed them for EPMA
analysis. Consequently, it becomes clear that geochemistry of pumices are rhyolitic and rich inalkaline component elements relatively (SiO2; 78.3wt%,NaO2; 3.18wt%, K2O; 3.79wt%). Next,
geochemistry of Nantaisan Shichihon-sakura/Imaichi tephra (Nt-S/I), in some tephra erupted around17.7+-1.38 ka,has slightly bimodal, and the group which K2O content is rather little (SiO2;
77.7wt%,NaO2; 3.23wt%,K2O; 3.97wt%) is similar to the geochemistry of pumices in Tephra1.
Nt-S/I is originated from Nantaisan, which belong to the Nikko volcanic area, west Tochigi
Prefecture and consisting of Shichihon-sakura pumice unit (SP; Kanto Roam Kenkyu Group, 1965) as
upper part and Imaichi pumice unit (IP; Kanto Roam Kenkyu Group, 1965) as lower part.These fall-out
pumice units involving scoria distribute toward east from the source mainly, and its correlatives
are found at the Kinu River Lowland area, around Mito and furthermore the Jyoban Coast (Machida andArai, 2003; Suzuki, 2011).As Nt-S/I correlatives in Tephra 1 are almost pumice grains and there aremuch contaminated grains in fine materials of Tephra 1,it seems less possibly that Nt-S/I tephra
fell out at this site off Kashima. We suppose, as a highly probable transportation process, that
Nt-S/I pumice grains falling out at sea off Mito, or carried out to the Pacific by the Kinu Riverand the Naka River are transported off Kashima by marine current.
Then, Suzuki (2011) reported that Asama Itahana Yellow tephra (As-YP; Machida and Arai, 2003) foundjust under Nt-S/I around Nikko area. Twenty three tephra beds in this core Aoki (2008) reported are
visible tephra beds, so As-YP would be bearing under Tephra 1 that correlated to Nt-S/I.

©2016. Japan Geoscience Union. All Right Reserved.

- HQR15-04 -HQR15-04

Japan Geoscience Union Meeting 2016

Keywords: Nantaisan Shichihon-sakura/Imaichi tephra, tephrostratigraphy, oxygen isotopic
stratigraphy, IMAGES, marine core, off Kashima©2016. Japan Geoscience Union. All Right Reserved.

- HQR15-04 -HQR15-05

Japan Geoscience Union Meeting 2016

Reexamination of the eruptive age of Late Pleistocene widespread DKP tephra by using
MD01-2421 core collected off the Kashima-Pacific coast, Japan*Takehiko Suzuki1, Kaori Aoki2, Tadashi Maruyama3, Masaru Saitou4
1.Faculty of Urban Environmental Sciences, Tokyo Metropolitan University, 2.Rissho University,
3.Institute of Earthquake and Volcano Geology, National Institute of Advanced Industrial Scienceand Technology, 4.DIA CONSULTANTS CO., Ltd.
DKP tephra derived from the Daisen volcano, west Japan, is one of the most important Late
Pleistocene widespread tephras because it covers a broad area including Central Japan, North Kanto
and South Tohoku where inland fluvial terraces formed in the Last Glacial Period are welldeveloped. It also plays an important role as a useful key bed for evaluating paleo-climate changes
and crustal movement and so on in this period. However, the age of DKP is highly controversial
since the end of 1970s, that is, 45–47 ka (Machida and Arai, 1979), ca. 50 ka (Takemoto, 1991),
50–52 ka (Nakamura et al., 1992), >55 ka (Machida and Arai, 2003), 49–53 ka (Yamamoto and Hasebe,2014), 55–66 ka (Suzuki et al., 2016). In order to determine the reliable eruptive age of DKP, we
examined MD01-2421 core collected off the Kashima-Pacific coast, Japan.
Hakone-Tokyo Tephra (Hk-TP) is crucial tephra for determination of the eruptive age of DKP because
it is positioning immediately above DKP. However, characteristic properties for the identificationof DKP in volcanic soil deposits just above Hk-TP are insufficient, and the age of Hk-TP have been
estimated to be older (e.g. 66.0±5.5 ka: Aoki et al., 2008) than previous studies.
In this study, we detected fine white pumice clasts (0.2 mm in diameter) with characteristic
properties similar to those of DKP at a depth of 2018.20–2020.45 cm (93.45 cm above Hk-TP).
Refractive indices of volcanic glass shards is 1.508-1.514, and major element composition (wt.%;
mean and standard deviation for 15 measurements) in those is SiO2: 73.57 (0.34), Al2O3: 14.74(0.14)，FeO: 1.90 (0.12)，CaO: 2.12 (0.05), K2O: 2.55 (0.09), Na2O: 4.13 (0.34). These features arequite similar to those of well preserve DKP tephras in terrestrial sediments collected in Toyama
and Fukushima Prefectures. Stratigraphic position where these pumice clasts were detected is dated
at 60.08±5.68 ka (MIS 4.0–4.22) due to oxygen isotope stratigraphies shown by Oba et al. (2006) andMartinson et al. (1987).
Keywords: Widespread tephra, Late Pleistocene, DKP, marine tephra©2016. Japan Geoscience Union. All Right Reserved.

- HQR15-05 -HQR15-06

Japan Geoscience Union Meeting 2016

Reconstruction of sedimentation rates during the last ca. 50,000 years using multiple
cores in Lake Suigetsu, central Japan*Keitaro Yamada1, Takeshi Nakagawa2, Megumi Saito-Kato3, Keiji Takemura1, . SG14 coring members
1.Kyoto University, 2.Ritsumeikan University, 3.National Museum of Nature and Science
Lake Suigetsu in Fukui Prefecture, central Japan, is a one of the tectonic lake located in a
subsiding area related to the active Mikata reverse Fault (Okada, 2004). The sediments of Lake
Suigetsu annually laminated over the last ca.70 kyr (Nakagawa et al., 2012) with a significant
number of event layers (e.g. associated with earthquakes and floods; Schlolaut et al., 2014), which
record paleoclimate and palaeoenvironment changes. Two long cores (SG93, SG06) have previously been
recovered from the centre of the lake in 1993 and 2006, respectively, and an exceptionally precise
age model has been established for the cores through a combination of over 800 radiocarbon dates
and high precision varve counting (Staff et al., 2011; Marshall et al., 2012; Schlolaut et al.,2012; Bronk Ramsey et al., 2012). Recently, new cores (SG14) were recovered by the Fukui prefecturefrom boreholes ca. 500 m to the east of the SG06 coring site. In this study, we report thosesedimentation rates of Lake Suigetsu during ca. 50,000 years and its triggers on the basis of thesecores and the precise age model.
The SG14 core was obtained from 4 separate boreholes (E, F, G, H) to ensure overlapping with eachother. Half cut sections of these cores were immediately photographed before oxidizing underprecisely controlled lighting conditions. Furthermore, long soft X-ray images were taken on 1 mlong giant thin-section slabs of these cores. On the basis of these images, we stratigraphicallycorrelated the SG14 core with the SG06 core at more than 300 points in ca. 70 m lengths using a
number of event layers to apply the precious age model of the SG06 core.
Focusing on the age of 0 to 50 ka, the SG14 core was deposited at 0.5 m/kyr and show strong
correlation with that of the SG06 in depth. The rate increases after 13 ka and has gradual several
thousand-year cycles. These cycles may relate to global environmental change. Furthermore, the rate
drastically increases at the some horizons, which are able to classify into two types on the basisof comparison with the rate of the SG06 core: synchronous type and asynchronous type. The
synchronous type increase the rate in each site at the same time, indicating the rate is likely
affected by relatively large-scale event. On the basis of the age model, one of the this type iscorrelative with Kanbun historical earthquake in 1662. Therefore, this type may be induced bytectonic event. The rate of asynchronous type is clearly different between each site, indicating
the rate is strongly affected by local event such as turbidites. As a result, we probably detected
global environmental changes, tectonic events, and local events on the basis of high precise
correlation between the SG14 and SG06 cores. Additional correlation data between the SG14 and SG06
are necessary in future research to improve understanding of the sedimentary process of Lake
Suigetsu.
Finally we thank the SG14 coring members of Richard A. STAFF, Ikuko KITABA, Junko KITAGAWA,
Tsuyoshi HARAGUCHI, Victoria C. SMITH, Danielle McLean, Katsuya GOTANDA ,Paul G. ALBERT, Masayuki
HYODO, Yoshiaki SUZUKI, Hayato MATSUSHITA, and Akiteru YAMAZAKI for sampling and other hard woks.
Keywords: sedimentation rate, Lake Suigetsu, varve, earthquake©2016. Japan Geoscience Union. All Right Reserved.

- HQR15-06 -HQR15-07

Japan Geoscience Union Meeting 2016

Temperature change in northern Japan during the last 6,700 years and the related humanactivity*Hodaka Kawahata1, Yoshiki Hatta1, Habu Junko2, Akihiro Yoshida3
1.Atmosphere Ocean Research Institute, the University of Tokyo, 2.University of California,
3.Kagoshima University
Marine coastal sediments provide a big advantage to have continuous record of both marine andterrestrial environments in their sedimentary sequence. In addition, high correlation between
atmospheric and sea surface temperature in bays present very unique opportunity to reconstructterrestrial temperature quantitatively. In this study we therefore collected one core fromsemi-closed bay in southern Hokkaido. We measured organic material of alkenone and analyzed pollen
assemblage to estimate temperature. Our goal was to reconstruct with high time resolution oftemperature in marine and adjacent terrestrial environments, to evaluate the process behind longand short term trend of temperature for the last 6000 years, and to understand the relationshipbetween climatic changes and the human activity including the rise/fall of the human population at
the Sannai-Maruyama site. This time Core St. 5 was collected rat a distance of only 7.8 km from thecoast and at a water depth of 65 m of Site 5 in Uchiura Bay during the research program by
Geological Survey of Hokkaido in 2010. Then we analyzed alkenone SST. It showed a variation of 8.7°C (maximum and minimum of 14.5 °C to 23.2 °C, respectively). The mean SST was 14.5 °C. The SSTs
gradually increased during the last 7000 years. The SST peaked in 4529 BC, 2546 BC, 759 AD and 1782
AD. Smaller peaked in 4057 BC, 3585BC, 3018BC, 1885BC, 1508 BC, 1035 BC, 469 BC, 122AD, 381AD, 1164
AD. Large temperature falls occurred in 4500-4000 BC, 2550-2000 BC and 760-1080AD.
Keywords: temperature, Jomon people, Climate©2016. Japan Geoscience Union. All Right Reserved.

- HQR15-07 -HQR15-08

Japan Geoscience Union Meeting 2016

Abrupt cooling event during the middle Holocene from pollen data of marine costal
sediments in Uchiura bay, northern Japan*Akihiro Yoshida1, Hodaka Kawahata2, Junko Habu3
1.Kagoshima University, 2.Tokyo University, 3.Research Institute for Humanity and Nature
Holocene climate records provide valuable information for inferring past interaction between humans
and environment. We present well dated pollen data covering the last 7,000 years from Uchiura bay
in southern Hokkaido, norther Japan, in order to better understand the change of human population
for the Jomon sites around northern Japan. In addition, we show the palaeoclimatic reconstructions
since the middle Holocene from the pollen data, using the best modern analogue technique (MAT). The
pollen-based quantitative palaeoclimatic data in Uchiura bay indicate that small-scale cooling
events took place at ca. 4.2-4.5 ka cal BP, 2.3-2.4 ka cal BP, and ca. 1.0-1.2 ka cal BP. From thedata, the temperature at ca. 4.2-4.5 ka cal BP drastically decreased about 1.5 °C. The cooling at
the period corresponds to the decrease of alkenone-SST in Uchiura bay and other palaeoclimaticrecords throughout East Asia. We can suggest that the abrupt cooling event at ca. 4.2-4.5 ka cal BP
influenced human activities and population during the Jomon period in northern Japan.
Keywords: pollen data, palaeoclimatic reconstruction , modern analogue technique , Uchiura bay,northern Japan©2016. Japan Geoscience Union. All Right Reserved.

- HQR15-08 -HQR15-09

Japan Geoscience Union Meeting 2016

Food Diversity, Climate Change and the Resilience of Subsistence-Settlement Systems: A
Case Study from the Jomon Period*Junko Habu1
1.Research Institute for Humanity and Nature
Archaeololgists have long been interested in the study of the mechanisms of long-term culturechange. Factors that involve specialization and centralization, such as domestification of plants,
technological developments and social competitions, have been proposed as prime movers for the"development" of human societies. Contrary to these interpretations, this presentation proposes ahypothesis that diversity and decentralization may be critical for maintaining long-termsustainability of human societies in the order of hundreds to tens of thousands of years. Using the
research outcomes of a Full Research Project "Long-term Sustainability through Place-based,
Small-scale Economies: Approaches from Historical Ecology" at the Research Institute for Humanity
and Nature, Kyoto, this presentation aims at testing the hypothesis discribed above and examining
the long-term impacts of the loss of subsistence/food diversity in relation to other environmental
and cultural factors. The theoretical genesis of this project is the approach of historicalecology, which conducts comprehensive research on long-term culture change while emphasizing theimpact of human activities on the environment.
Results of lithic assemblage analysis, residue analysis on pottery, starch grains analysis on stone
tools, stable isotope analysis of skeletal remains and faunal remains, and AMS radiocarbon datingof skeletal remains are used to understand changes through time in food and subsistence diversity
and other cultural factors. These results are compared against the patterns and timings of climatechange identified through pollen analysis and alkenone sea surface temperature analysis. In
addition, GIS analyses are conducted to understand changes in settlement size and site distribution
patterns. Simulation studies of population dynamics of the Early to Late Jomon periods using SPD(summed probability distribution) analysis are also conducted.
Keywords: Food diversity, Climate change, Resilience, Jomon, Subsistence-settlement systems©2016. Japan Geoscience Union. All Right Reserved.

- HQR15-09 -HQR15-10

Japan Geoscience Union Meeting 2016

Long-time sastainability of prehistric subsistence of Jomon culture.
*Minoru YONEDA1, Takashi NARA2, Junmei SAWADA2
1.The University Museum, The University of Tokyo, 2.Niigata University of Health and Welfare
In order to reconstruct the variability of dietary habit among individuals and/or population of
Jomon periods, we are investigating the carbon and nitrogen isotope ratios in human bones from theTokyo Bay area and Aomori prefecture. One of the main goals is the comparison of Jomon dietary
habits in the latter part of Jomon periods in light of diversity, variability and sustainability.
Our testing hypothesis is that “the Middle Jomon started an intensive exploitation of plantresources and this strategy decreased the resilience of Jomon subsistence and 'a population
collapse' was observed in the Late Jomon period”. Now we are working on the series of Middle, Late,and Final Jomon skeletons (ca. 6 to 3 thousand years BP) from the Tokyo Bay area and Aomori
prefecture. The comparison between two Jomon sub-groups provide an insight into the response of
Jomon hunter-gatherers against cooling and regression events in this periods and social change intime series as well by comparing diversitie of diet among social members.
We would liket discuss the change of carbon and nitrogen isotope ratios in both ecological andsocial points of view.
Keywords: physical anthropology, prehistoric archaeology, isotope ecology©2016. Japan Geoscience Union. All Right Reserved.

- HQR15-10 -HQR15-11

Japan Geoscience Union Meeting 2016

The estimation of formation ages of fans at the eastern foot of Ikeda Mountains, central
Japan by the AMS14C dating and re-examination of average slip rates of Ikedayama fault*Tomohiro Takaba1, Hidetsugu Yoshida2, Toshihiko Sugai3
1.Depertment of Geography, Graduate School of Arts and Letters, Meiji University, 2.Depertment ofGeography, Meiji University, 3.Depertment of Natural Environment Studies, Institute of Natural
Environment Studies, Graduate School of Frontier Scinece, The University of Tokyo
A number of small fans have been developed at the eastern foot of Ikedayama Mountain of Ibuki
Mountains, central Japan. These fans are regarded as useful landforms in evaluating the reverse
fault activity of Ikedayama fault, dividing from the Nobi Plain, because it runs across theterraces with different ages. The average slip rates of Ikedayama fault, with a length of ca.16 km,
was once evaluated as 0.8-0.9 m/1,000 years (Gifu Prefacture, 1998, 1999, and AIST), and recently,
re-evaluated as 0.4-0.7 m/1,000 years in the area of northern margin, and 1.3-1.7 m/1,000 years ormore in the central part of fult (Ishimura, 2010). On the other hand, we have been carried out AMS
14

C dating of humus developed on the debris-flow fan deposits, and classification of the terrace

landforms in order to clarify the geomorphologic development process of these small fans. Our
results show the estimated age of terrace surface as 17-20ka (upper surface), 10ka (middle surface(upper)), 9ka (middle surface (lower)) and 8ka (lower surface) (Takaba et al., 2016). These ages
clearly differ from those estimated by the detection of crypto-tephras from the topsoil (Ishimura,2010). Therefore, we consider the necessity for re-examination of the activities of Ikedayama
fault, again. In this study, using the Fundamental Geospatial Data (Digital Elevation Model of 5 mmesh) by the Geospatial Information Authority of Japan, the fault vertical offsets on the terrace
surfaces of same age were measured. They are 9-10.5 m in the upper surface of the northmost part,
10-11 m in the middle surface (upper), 8-10 m in the middle surface (lower), 9-11 m in the middle
surface of the central (lower), 6-7 m in the lower surface, 2-2.5 m in the lower surface of thesouth, and 1.5-2 m in the lower surface. Based on the estimated ages of the terrace serfaces andtheir vertical offsets above, the average slip rates were calculated to 0.45-0.53 m/1,000 years(the upper surface), 1.0-1.1 m/1,000 years (the middle surface (upper)), 0.89-1.18 m/1,000 years(the middle surface) in the north part of fault, and 1.00-1.29 m/1,000 years (the middle (lower)
surface), 0.71-0.88 m/1,000 years (the lower surface) in the central part of fault, and 0.18-0.25
m/1,000 years and,0.24-0.32 m/1,000 years (the lower surfaces) in the south part of fault. Although
the lower values should be discounted, the representative average slip rate of Ikedayama fault canbe 0.8-1.2 m / 1,000 years, close to the estimate by the Gifu Prefecture (1998, 1999).
References
Gifu Prefacture (1998) Survey on Ikedayama fault, Earthquake relationship basic research grant
results report fiscal year 1997, 97p.
Gifu Prefacture (1999) Survey on Ikedayama fault, Earthquake relationship basic research grant
results report fiscal year 1998, 86p.
Ishimura, D. (2010) Chronology of fluvial terraces and fault activities in and around the
Sekigahara region, central Japan, The Quaternary Research, 49, 225-270
Takaba, T. Yoshida, H. and Sugai, T. (2016) Chronology of terraces of debris-flow fans at the footof Ikeda Mountains, Gifu, central Japan, The Association of Japanese Geographers Spring Meeting2016 reseach announcement
Keywords: Ikedayama Fault, Average Slip Rates, Offsets©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

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Japan Geoscience Union Meeting 2016

Quaternary activity of the Erciyes fault southeast of the Kayseri basin, Turkey*Koji Okumura1, Yuichi S. Hayakawa2, Ryoichi Contain3
1.Graduate School of Letters, Hiroshima University, 2.Center for Spatial Information Science, The
University of Tokyo, 3.Notre Dame Seishin University
The Erciyes fault in southeast of the Kayseri basin is one of the most significant Quaternaryfaults in Central Anatolia, together with the Ecemis fault and the Tuz Golu fault. Emre et al.
(2011: New active fault maps of Turkey, Kayseri sheet) mapped about 100 km long strands of the
Erciyes fault with its 30 km long southwestery section run across the center of the Erciyes
volcano. A M 7+ earthquake from the fault might be a big threat for the 1.5 million people in
Kayseri basin, but little has been known about its Quaternary activity and the reality of the fault
traces on the volcanic edifice. We have studied Plio-Pleistocene ignimbrites and Quaternary
sediments in southeast of the Kayseri basin and recognized significant dip-slip separation in thecentral portion east of Kayseri city and Quaternary left-lateral (?) strike-slip activities in thenortheastern portion of the fault as they are mapped by Emre et al. (2011). Along with fieldobservations, we applied a high-definition topographic mapping approach using a small unmanned
aerial vehicle (sUAV) and structure-from-motion (SfM) multi-view stereo photogrammetry. This
enabled us to generate topographic data with a resolution of centimeters for a range of hundreds ofmeters, which were used to identify small topographic features such as scarps on the land
surface.The Valibabatepe (or the Incesu) ignimbrite dated as 2.52±0.49 Ma (Aydar et al., 2012) or
2.6 to 3.0 Ma (Le Penne et al., 2005) is a very distinctive extremely densely welded thin (~5 m)
and hard ignimbrite layer capping the plateaus around western Kayseri basin. At Gesi Guney, 18 km
ENE of Kayseri city center, the Incesu ignimbrite is distributed both on the 1340 m a.s.l. plateau
and on the 1250--1270 m a.s.l. upland below the plateau. The ~70 m high scarp clearly demonstrates
the Quaternary activity of the Erciyes fault. At the base of the scarp, talus deposits arejuxtaposed with bedrock ignimbrite with an apparently NW dipping normal fault. An alluvial fan
formed by a gully cutting into the Incesu plateau is also deformed by the fault. Around Gunesli, 25
km northeast of Kayseri city center, a fluvial gravel and sand layer that postdates the
Valibabatepe ignimbrite is distributed along the foot of upland consists of pyroclastic flows older
than the Valibabatepe ignimbrite. The fluvial gravel and sand layer, together with underlying
pyroclastic flow deposits and an overlying pumice fall layer, is truncated by a swarm of verticalfaults and dragged into the fault zone. The fault zone structure indicates the faults are
strike-slip faults. These faults are located about 100 m inside the upland there is no offset
topography on top of the faults. The ages of the faulted tephra layers are not known yet, but it isclear that significant strike-slip fault movement occurred during Quaternary after the Valibabatepe
ignimbrite.
Keywords: active fault, pyroclastic flow deposits, Kayseri©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Geomorphological evolution of Notsukesaki barrier spits resulting from seismotectonics
along the southern Kuril Trench
Kazuaki Watanabe1, *Futoshi Nanayama1, Kiyoyuki Shigeno2, Takeshi Hasegawa3, Kazuto Ishiwata4,
Tetsuya Ono5
1.Geological Survey of Japan, AIST, 2.Meiji Consultant Co., Ltd., 3.Ibaraki Univ., 4.BetsukaiMuseum, 5.Po-gawa Historic Site and Natural Park, Shibetsu Town
An active barrier system is developed in the Nemuro Bay area along the Okhotsk Sea in eastern
Hokkaido, Japan. This presently rare feature consists of a lagoon (the Notsuke Bay), a flood tidaldelta, barrier spits, and a tidal inlet that opens into the outer sea of Nemuro Bay and the Sea of
Okhotsk. The Notsukesaki barrier spits are active along the northeastern side of the Notsuke Bay,and four spit groups (NBS1˜NBS4) can be observed clearly. Using geomorphological andsedimentological methods, we analyzed Holocene sediments around the Chashikotsu lowland andNatsukesaki barrier spits. We dated them using radiocarbon and tephrochronological methods. The
Notsukesaki barrier system has been established before 4.0 ka presumed by Ma-d tephra. NBS1, themodern transgressive spit was formed after the 17th century, and NBS2 was caused by the lastseismic uplift in the 17th century because Ta-a and Ko-c2 tephra covered the surface of NBS2. NBS3
was uplifted in the 12˜13th century, and NBS4 was caused by seismic uplift maybe before the 10th
century because Ma-b tephra covered the surface of NBS4. These great earthquakes (Mw8.5˜9.1) haveoccurred at an approximate 500-year interval along the southern Kuril subduction zone. Coastal
areas were raised by 3~ m during or just after the earthquakes due to postseismic displacement.
Conversely, land subsidence has been ongoing at a rate of about 1.5 mm/year since the 17th century.
We conclude that the geomorphological evolution of the Notsuke barrier system has been controlled
by the seismotectonics along the Kuril subduction zone.
Keywords: Notsukesaki barrier spits, seismotectonics, southern Kuril trench, geomorphologicalevolution, eastern Hokkaido©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Stratigraphy of the Middle to Late Pleistocene in the southwest Hokkaido, Japan*Akihiro Yokota1, Reisuke Kondo2
1.Meiji Consultant Co., Ltd, 2.Educational Development Center, Kogakkan University
The Middle to Late Pleistocene Setana Formation and Ohyachi Formation is distributed in Setana
Plain, southwestern Hokkaido, North Japan. The Setana Formation consists of tuffaceous sandstone in
Setana Plain. This is sandwiched by the Ohya Formation and Kuromatunai Formation.
Sedimentary age of Setana Formation has been estimated to be 1.2 Ma to 0.6 Ma by biostratigraphic
investigation. But there aren’t a lot of previous research about Stratigraphic Relation between
Ohyachi Formation and Setana Formation and that’s geomorphic development.
Recently, Kondo et al. (2016) got Setana Formation’s and Ohyachi Formation’s conclusive age by OSL.
The purpose of this study is to clarify the Stratigraphic Relation and the paleo-environment by
Sedimentary age.
Keywords: southwestern Hokkaido, Setana Formation, Stratigraphy©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Characteristics and Development Processes of Wetlands on Large-scale Landslide in Ou
Mountain Range, NE Japan*Natsuki Sasaki1, Toshihiko Sugai1
1.Graduate School of Frontier Science, The University of Tokyo
Quaternary volcanoes in the Ou Mountains, northeastern Japan, are occasionally dissected bylarge-scale landslides with their areas greater than 1 km2. On these landslide bodies various-size
wetlands have been formed in the landslide depressions and contribute to creating mosaic landscapesand biodiversity of landslide areas with the steep scarps and forests. Since establishment ages of
wetlands on landslide bodies reflect the timing of landslide activities, simultaneity of wetland
formation in a single active landslide is inferred. However a large landslide contains coexisting
wetlands of various development stages, including ponds and peat bogs. This contributes to further
diversity of their landscapes and biota. This study examines geomorphological controls on the
distribution and development of wetlands on large-scale landslides in the Ou Mountains.
We mapped in detail the microtopography of the landslides and identified ponds using color aerial
photographs (1 : 18,000 and 1 : 15,000 scale) taken by the Geographical Survey Institute in 1976.
We then calculated the slope inclination and the curvature, and mapped the drainage system from the
GSI (the Geospatial Information Authority of Japan) 5-m or 10-m digital elevation models (DEM)
using ArcGIS.
We selected 3 landslides in the Hachimantai Volcanic Groups and 2 in the Funagata Volcanic groups.
These landslides have degraded caprock structure of the soft Neogene tuff covered with lava flows.
The landslides on the Hachimantai are rotational ones that feature arcshaped scarps and stepped
terrain in their upper parts. They have more fragmentary structures in their middle and lower
parts. The secondary landslides commonly deform the feet of main landslides and contribute further
to the undulating surface. Whereas these on the Funagata Mountain are translational landslides thatfeature rectilinear shaped scarps and constant height of block structures due to tensile stress.
Wetland distributions are controlled by microtopography of landslide bodies, and the wetland area
is determined by the size of the depressions. The wetlands are mostly elliptical shape with longaxes parallel to the linear depressions. On the Hachimantai, the wetlands in the middle and lower
part of the landslide bodies tend to be smaller due to fragmentary topography. On the secondary
landslides, a few wetlands stand only at the foot of the main scarps or in the depression between
pressure ridges, because the soft material (earth flow) could not form depressions perpendicular tothe slope direction. On the Funagata Mountain, the wetlands stand in the depressions between the
scarps and in the cracks that are widely scattered over the landslide bodies.
All landslides in this study contain both ponds and peat bogs, different development stages.
Sediment accumulation, connecting drainage channels and shortage of water recharge are considered
to be major factors of wetland development from ponds to forests via peat bogs. The superposition
map of the wetland distribution and the drainage system draws that the greater part of wetlands areconnected to drainages whether water constantly flows or not through them. The peat bogs or forests(the latter stage of wetland development) tend to connect to higher order deeper streams. Therefore
the degree of fluvial dissection of landslide bodies controls wetland development stage on thelandslides. Landslide dams, such as the Nagamuma on the Funagata Mountain, with abundant recharge
water from the upstream area could continue to be pond for a longer time than the other wetlands.
Keywords: wetland distribution, landslide, development process, Ou mountains©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

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Japan Geoscience Union Meeting 2016

Relationship between Holocene sequence of the Tsuya plain and subsidence trend along thesouthern Sanriku coast, northeast Japan*Yuichi Niwa1, Toshihiko Sugai2, Yoshiaki Matsushima3
1.IRIDeS, Tohoku Univ., 2.Univ. of Tokyo, 3.Kanagawa Prefectural Museum of Natural History
The Sanriku coast has some small alluvial plains at environments of rias coast. Althoughlithofacies of the incised valley fills is reported in some alluvial plains in the Sanriku area,
formation process of the valley fills had not been discussed on the basis of many radiocarbon ages
in the previous studies since 1980’s . Knowledge of incised valley fills with many radiocarbon ages
can be basic and important data for not only understanding of formation process of alluvial plain
but also clarification of tectonic history in this area. A sediment core, TY1, was acquired fromlower reach of the Tsuya Plain, northeast Japan. Core sediments show shallow marine succession
influenced by the Holocene sea-level change. On the basis of twelve radiocarbon ages, accumulation
rate is high (> 10 mm/yr) at 9,000 to 7,100 cal BP, low (ca. 0.5 mm/yr) at 7,100 to 2,800 cal BP,
and high (3 –5 mm/yr) after 2,800 cal BP. High accumulation rate at early to middle Holocene
indicates sedimentation from seaward area during the term of marine transgression. In the
regressive phase since the middle Holocene, low accumulation rate in the deltafront deposits andhigh accumulation rate in the delta plain deposits shows most of sediments are deposited in delta
plain area, indicating continuous rising trend of relative sea-level (RSL) during the Holocene.
This suggested rising trend of RSL is consistent with previously reported Holocene subsidence inthe southern Sanriku coast.
Keywords: Sanriku coast, Tsuya plain, Holocene sequence, radiocarbon dating, subsidence©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Tephras and fossil pollen stratigraphy of all-cores drilled in the eastern margin of the
Aizu basin, Northeast Japan*Takeshi Ishihara1, Takehiko Suzuki2, Misao Hongo3, Youhei Uchida1
1.National Institute of Advanced Industrial Science and Technology, 2.Faculty of Urban
Environmental Sciences, Tokyo Metropolitan University, 3.Alps Technical Research Laboratory Co.,Ltd.
1. Introduction
Aizu Basin is one of tectonic basins aligning with north-south direction in the south part ofNortheast Japan. Along the west and east margin of the basin, the West Aizu Basin Fault Zone andthe East Aizu Basin Fault Zone, active reverse faults, stretches respectively (e.g. Ikeda et al.,2002). Geomorphic development of the basin since Miocene has been discussed by Suzuki et al.
(1977), Yamamoto (2006) and so on. Activity of both fault zones during the last a few ten thousand
years was reported by Fukushima Prefecture (2002) and AIST (2007). Kuriyama and Suzuki (2012) andSuzuki et al. (2016) discussed late Quaternary tephrostratigraphy based on analysis of a drillingcore (AB-12-2 core, 179.08 m asl) and another boring cores in the western part of the basin.
In this study, we drilled two all-cores (GS-SOK-1, 175.99 m asl, 130 m depth; GS-AZU-1, 208.36 masl, 100 m depth) in the eastern margin of the Aizu basin. Ishihara et al. (2015) reported analysisof tephras and radiocarbon ages of the GS-SOK-1 core. In this report, we show fossil pollen
stratigraphy of the GS-SOK-1 core, and lithofacies of the GS-AZU-1 core and detected tephras.
2. Fossil pollen stratigraphy of the GS-SOK-1 core
15 muddy sediment samples were collected from GS-SOK-1. The Pleistocene sediments in the GS-SOK-1
were divided into 10 local pollen assemblage zones (SOK-I, -II…, and –X, in ascending order) an
informal nomenclature by a distinctive assemblage of taxa, indicating local environmental
conditions as a rudimentary biostratigraphic classification. We compared these zones with local
fossil pollen assemblage zones of Nanaorezaka Formation (lower Pleistocene) and Todera Formation(middle Pleistocene) in the western margin of the Aizu Basin (Suzuki et al., 1990).
Because Tertiary flora (Metasequoia, Keteleeria, Carya, Liquidambar) are slightly included in the
SOK-I zone (the depth of 111.1 ~ 126.8 m), the SOK-I zone can be correlated with TD-I zone
(Nanaorezaka Formation; Suzuki et al., 1990). SOK-II, -III, and -IV zones (78.1 ~ 104.3 m depth)
can be compared with TD-II ~ -IV, -V ~ -VI, and -VII zones (Todera Formation; Suzuki et al.,1990), respectively. SOK-V ~ -X zones (23.5 ~ 72.9 m depth) includes Fagus and Quercus dominantly(except SOK-V zone), whereas Pinaceae are detected dominantly in the upper part of Todera Formationin Suzuki et al. (1990). Thus, it is suggested that these zones are younger formation than the
Todera Formation.
3. Lithofacies of the GS-AZU-1 core and detected tephras
In the depth from surface to 52.5 m, dark grey or green grey silt, peat, and sand are dominant
excepting gravel layer in the depth of 36.5 ~ 41.6 m. Several volcanic ash and pumice layer aredetected. Characteristics of volcanic glass shards and containing colored mineral indicates that AT(29-30 ka; Machida, 2011) is included in the depth of 13.35 ~ 13.38 m and Aso-4 (87 ka; Aoki et al., 2008) is in 30.25 ~ 30.30 m. A lot of biotite are contained in a pumice layer (34.10 ~ 35.10 m)
and a volcanic ash layer (52.35 ~ 52.40 m), indicating that they were supplied from the Oku-Aizu(Numazawa or Sunagohara) Caldera.
From 52.5 m to 91.3 m depth, green grey or yellow brown sandy silt or sand with pumices andphenocrysts mineral such as quartz are dominant and a thin gravel layer is at the depth of 76.3 ~78.7 m. It is suggested that these sandy silt and sand layers are pyroclastic flow sediments and©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

their rework sediments. Below 91.3 m the core consists of yellow brown or grey white volcanic sandand silt. The pyroclastic flow sediments can be correlated with the Shirakawa pyroclastic flow
units (lower Pleistocene; Yoshida and Takahashi, 1991; Yamamoto, 2006) if above volcanic ash layer
is the tephra from the Oku-Aizu Caldera.
Keywords: Aizu Basin, Boring, Tephra, Fossil pollen, Quaternary©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Tephra of the Upper Pleistocene Joso Formation, Shimosa Group in the western Tsukuba
Upland, central Kanto Plain*Daichi Akiyama1, Hiroko Okazaki2, Hiroomi Nakazato3, Shinzou Ooi4, Toshihiko Sugai1
1.Department of Natural Environmental Studies, Institute of Environmental Studies, Graduate Schoolof Frontier Science, The University of Tokyo, 2.Division of Earth Science, Natural History andInstitute, Chiba, 3.National Institute for Rural Engineering, 4.Research Institute of Geology andGeoinformation, Geological Survey of Japan
Most of the terraces in the Kanto Plain were formed on and after Marine oxygen-Isotope Stage (MIS)
5e. Palaeo-Tokyo Bay spreaded in MIS 5e was becoming regression gradually. The geomorphic surfacesof MIS 5e were formed by Kioroshi Formation, and the geomorphic surfaces of MIS 5c and MIS 5a wereformed by Joso Formation, in the Tsukuba Upland. Joso Formation has been classified by geomorphic
surface classification, tephrochronology and sedimentary facies analysis. The purpose of this study
is to make the improvement of a time axis in Joso formation from sedimentary facies analysis andtephrochronology targeted for the western Tsukuba Upland over the central Ibaraki Prefecture. The
results, 2 to 4 sedimentary units of the marsh and channel facies are recognized Joso Formation in
the Ryugasaki Lower surface (Ikeda et al., 1982) , Joso surface (Unozawa et al., 1988) and Joso,
Ishizuka surface (Ooi et al., 2013) . Hk-TP tephra (66ka; Aoki et al., 2008) is recognized from
Kanto loam Formation. On-Ng tephra (about 85ka; Nagahashi et al., 2007) or On-Pm1 tephra (about
96ka; Aoki et al., 2008) , and so on were confirmed from Joso Formation by the mineral composition
and the chemical composition of the glass. It's expected that this study offers essential datum
about the landform evolution in surrounding Upland and the Joso Formation study.
Reference
Akira Unozawa, Ichiyo Isobe, Hidenori Endo, Yuhsaku Taguchi, Shigeru Nagai, Takemasa Ishii, Teruo
Aihara and Shigefumi Oka (1988) Explanatory Text of the Environmental Geologic Map of the Tsukuba
Science City and its surroundings. Geological Survey of Japan, 139p. (in Japanese)
Hiroshi Ikeda, Kaori Mizutani, Yoichi Sonoda and Fujiko Iseya (1982) The Landform Evolution of the
TsukubaUpland -The Bird Foot Delta of "Palaeo Kasumigaura"-. Tsukuba no Kankyo Kenkyu, 6, 150-156. (inJapanese)
Kaori Aoki, Tomohisa Irino and Tadamichi Oba (2008) Late Pleistocene tephrostratigraphy of thesediment core MD01-2421 collected off the Kashima coast, Japan. The Quaternary Research (Daiyonki

kenkyu) , 47, 391-407. (in Japanese)
Shinzou Ooi, Nobuo Sairenji, Yoshiharu Yokoyama and Hisao Ando (2013) Re-examination of Terrace
Surface Division of the Hitachi Terraces, Ibaraki Prefecture. Bull. Ibaraki Nat. Mus., 16, 51-56.
(in Japanese)
Yoshitaka Nagahashi, Takako Sato, Yoshihiro Takeshita, Takaharu Tawara and Fujio Kumon (2007)
Stratigraphy and Chronology of Widespread Tephra Beds Intercalated in the TKN-2004 Core SedimentObtained from the Takano Formation, Central Japan. The Quaternary Research (Daiyonki kenkyu) , 46,
305-325. (in Japanese)
Keywords: Kanto Plain, Tsukuba Upland, geomorphic surface, Upper Pleistocene, Joso Formation,
tephra©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Shallow subsurface structure in Magame - Katakai area, Kujukuri coastal plain, Chiba
prefecture*Kazuo Yamaguchi1, Shinobu Ito1
1.Geological Survey of Japan, AIST
A shallow seismic reflection survey was conducted in the Kujukuri coastal plain, Chiba prefecture,targeting between a dozen meters and 300 m in depth to reveal the location and shape of buried
valley topography inferred below the Alluvial sediment. The survey area is along the coast between
Magame and Katakai of Kujukuri town where a buried valley is inferred from an existing geologicalmap. The survey parameters are as follows. Line length:4486m, seismic source:P-wave Yuatsu
impactor(JMI200), vertical stack:10, source point interval:2m, no. of source point:2242,
receiver:GS20-DM(28Hz single), receiver point interval:2m, no. of receiver point:2244, spread:rollalong from the first to 48th station for 192 fixed receivers, maximum offset:382m, recorder:DSS-12,
no. of recording ch:192. First breaks arrive to the maximum offset and the deepest reflection waves
appear down to 500ms in two way time in the vertical stacked and gained shot records. Source andreceiver couplings to the ground seem good on a sandy beach. Reflectors are perceived between adozen ms and 250ms in the CMP stacked time section. A reflector is strong and continuous, dips
northward very gently between 20ms and 30ms in the whole seismic section. It seems obscure at two
parts. Assuming that the velocity is 1.6km/s, this reflector is between -16m and -24m below sea
level. This is 10m to 20m shallower than the Alluvial depths of the above geological map, butalmost the same as those of the compiled boring data. This reflector is considered as the Alluvial
base. In the southern obscure part, first breaks of near offset traces are superimposed by coherent
noise. Discontinuous reflectors of 100m to 200m in length exist between 40ms and 70ms dispersively.
These may have something to do with natural gas (Uwa gas). Reflectors are obsucure between 100ms
and 170ms and reflectors are strong and uneven between 170ms and 250ms. Below the Alluvial sedimentare strata of the Kazusa group.
Keywords: Kujukuri coastal plain, seismic reflection survey, Alluvial base, buried valley©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

On-Pm1 tephra and marine deposits covering the tephra in the Choshi district, eastern
Kanto Plain*Hiroomi Nakazato1, Masakazu Nara2, Hiroko Okazaki3, Kiyohide Mizuno4, Hisatoshi Ito5
1.NARO, 2.Kouchi Univ., 3.Natural History Museum and Institute, Chiba, 4.AIST, 5.CRIEPIIn the Choshi district, eastern Kanto Plain, Shimosa Upper Terraces are widly distributed which arecomposed by the Katori Formation correlated with the Kioroshi Formation of the Shimosa Group.
Shimosa Lower Terraces and younger geomorphologic surfaces are distributed in the east side of the
Choshi district (Sugihara, 1976; 2000; 2008). Nakazato et al. (2015) detected the tephra thatabundantly contained pumice type volcanic glass and hornblende. They showed the possibility of thecorrelation between the tephra and On-Pm1, based on the refractive indices and chemicalcompositions of the volcanic glass and hornblende.
The Zircon U-Pb dating using LA-ICP-MS (Ito, 2014) was applied to the tephra in this study. As aresult, the obtained age of 100±60 ka improved the reliability of the correlation between thetephra and On-Pm1.
The outcrop where the tephra was detected shows the following stratigraphy: mud and sand stone of
the Kasuga Formation of the Inubo Group, unconformity, shoreface sand, terrestrial mud interbedding
the tephra (On-Pm1), shoreface sand with Macaronichnus isp., beach sand, fluvial deposits, Younger
Kanto Loam and Holocene dune deposits in ascending order. The age of marine sand overlying theOn-Pm1(95.7±5.3ka: Aoki et al., 2008) is more likely to be MIS5a.
Reexamination is necessary about the geomorphic and geotectonic history in this district because it
has been assumed that the MIS5a surfaces are distributed in lower altitude area than this point.
REFERENCES
Ito, H. (2014) Journal of Volcanology and Geothermal Research 289, 210–223.
Nakazato, H. et al. (2015) Abstracts, Japan Association for Quaternary Research 45,8-8.
Sugihara, S. (1976) Proceeding, Association of Japanese Geographers 10, 282-283.
Sugihara, S. (2000) Regional Geomorphology of the Japanese Islands vol. 4 Geomorphology of Kanto
and Izu- Ogasawara, 214-232, Univ. of Tokyo Press.
Sugihara, S. (2008): Regional Geology of Japan vol.3 Kanto, 322-325, Asakura Pub. .
Keywords: MIS5c, tephra, geomorphic surface©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Evolution process of the oyster reef and the ecology in Sanzanze, northeast Tokyo bay*Marie Noguchi1, Takafumi Kuroda, Kentaro Nakamura1, Kunihiko Endo2
1.Paleo Labo co.,ltd., 2.Nihon Univ.
Living oyster reefs were first found about early 2000s at Sanbanze, a sandy and muddy tidal flat inFunabashi City at the northeast end of Tokyo Bay. Large reefs of Crassostrea gigas emerged only at
the lowest point of spring tide, attracting public attention. After the peak of the development of
the oyster reefs in 2008, the activity started to decline in 2009 and the ecosystem have beenchanged. The evolution process of the ecosystem, and its response to environmental conditions
around the reefs, are key to understanding the present ecosystem, and also the environmental
changes.
Oyster reefs, and also size and shape of individual oyster shells must be influenced by suchenvironmental factors as nutrient salt, water temperature and habitat density in addition toweather condition, salinity, turbidity and so on (Chinzei, 1982, etc.).
In this study we investigate the relationship among changes in morphology through the growth ofoyster reefs and individual shells, evolution process of the reefs and environmental factors in andaround the reefs.
Koike, H.(1980) Seasonal dating by growth line counting of the clam, Meretrix lusoria. The
university museum, University of Tokyo, Bulletin, 18, 1-104.
Chinzei,K.(1982)Paleoecology of oysters (2). Fossil, 32, 19-27.
Noguchi, M., Kuroda, T., Endo, K.(2015)The oyster reefs of Sanbanze, in the tidal flat at
Funabashi, Chiba prefecture. Chuseki-so in Japan -Lastest Layer Bridging the Past and the Future-.
112-115, Fuzambo International.
Keywords: Tokyo bay, Oyster reef, Evolution process©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Depositional system of the early Pleistocene Inagi Formation, Kazusa Group in thenorthwest Tama Hills, central Japan*Yuma Kato1, Masaaki Shirai1
1.Tokyo Metropolitan University
The Tama Hills is composed by the late Pleistocene to middle Pleistocene Kazusa Group. The Kazusa
Group is typically distributed in the Central Boso Peninsula and composed underground of the Kanto
Plain and hills edging the plain. Fossils of mollusk, animals and plants occur from shallow marine
to non-marine Kazusa Group in the Tama Hills. Because, the Kazusa Group of the Tama Hills reflects
environmental changes such as eustacy, it is important to reconstruct the paleo-environmental
change the Early Pleistocene in the southern Kanto region with investigation of this area.
In this study, we focus on the Inagi Formation distributed in the northwest Tama Hills. The lower
to middle member of Inagi Formation are composed of gravel and sandy silt respectively, whereas theupper Member of is composed by sand (Takano 1994). Kikuchi (1984) estimated that the formation ofnorthwest Tama Hills is delta. The upper Member of Inagi Formation was estimated as delta topset.
Shirai and Imamura (2013) reported barrier island, estuarine and shoreface sediments from the upper
Member.
We estimated the depositional-environments of Inagi Formation with a facies analysis. The top ofsand layer from middle mud layer in Inagi formation divided to the estuary unit, barrier island
unit, shoreface-foreshore unit, Bay-head delta unit. Therefore, it was estimated that acomprehensive barrier island system include these four depositional units as a “small” estuay
whithin a “brood” back- barrier area. The estuary formed very broad bay accompanied by the barrier
island overlying of the bay-head delta unit on the shoreface-foreshore unit implies that estuary
and tidal-channel unite may have been formed.
Keywords: Facies analysis, Kazusa Group, Inagi Formation, estuary©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Holocene Landform Evolution at the South of Lake Idku, Northwest Nile Delta, Egypt,
Reconstructed from Settlement Location and Sediment Cores*Eimi Nishikawa1, Shigeko Haruyama2, Toshihiko Sugai1
1.Graduate School of Frontier Sciences, the University of Tokyo, 2.Graduate School of Bioresouces,
Mie University
1. Background & Objective
The Nile Delta has been formed in the mouth of Nile River, northern Egypt. It is said that Nile
Delta started to be formed at 7,000 yr BP when due to the decline of the speed of the worldwide
sea-level rise in post-glacial age sediment supply carried by river was piled in the depositional
space (Stanley and Warne, 1994). And in the case of Nile Delta, sea-level has been still rising in
1,000-year order and now it’s highest since post-glacial age caused by a compressive settling ofdelta deposits (Warne and Stanley, 1993). Besides it is a zone of arid environmental conditions
called desert climate. Therefore, Nile Delta has been modified complicatedly by various forms ofdepositions; fluvial, marine and aeolian. So it is significant to examine the micro-topographyusing higher resolution.
This study focused on specific site and aimed to reconstruct landform evolution from analysis ofthree sediment cores drilled by Cairo Univ. in 2012 and settlement location.
2. Study Sites & Methods
This study focused on the site of Lake Iduk in the east of the Rasheed branch. There is a Romanarchaeological site named Kom al-Diba’a in low land in the south of Iduk. It’s located two slightly
elevated flat hills which are about 6~8m high and 150~300m across. In this thesis the following
methods were used ; landform classification by satellite photography using GIS software, field
investigation of the study site, sedimentary facies analysis, soil color analysis, magnetic
susceptibility analysis, grain size analysis, elementary analysis, 14C dating.
3. Result & Discussion
Geomorphology and Geology of Kom al-Diba’a
By investigation of Kom al-Diba’a outcrop and sample analysis; magnetic susceptibility analysis andgrain size analysis, it is found that two slightly elevated flat hills are eolian sand dunes
consisting of well-sorted medium~fine sand. Besides, the upper part of the south hill’s outcrop isalternation of sand and silt which is assumed to be flood deposits.
Geomorphological Changes in the area of Lake Iduk
As a result of analysis about a sediment core drilled in former lagoon site of Lake Iduk, it can bedivided into the following three stages and estimated sedimentary age; AB-boundary: 3000~4000 yrBP,
BC-boundary: 1500~2000 yrBP. Thus, geomorphological changes in the area of Lake Iduk werereconstructed by these three stages. Thus, geomorphological changes in the area of Lake Iduk werereconstructed by these three units.
A: Iduk was connected to the Mediterranean Sea as a gulf. It was a depositional situation by
inflowing of beach ridge sediments due to waves or small transgression and of flood deposits
transported by the Nile. (Sand layer and element fluctuation)
B: Iduk was expanding especially to the east side caused by a compressive settling of delta
deposits and flooded land area reduced in consequence. (Reduction of sand layer and element
fluctuation)
C: Iduk was unconnected to the Mediterranean Sea due to beach ridge sediments transported from themouth of Rasheed branch by coastal current. (Decline of sulfur concentration)[References]©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Stanley, D.J. and Warne, A.G. (1994): Worldwide Initiation of Holocene Marine Deltas by
Deceleration of Sea-Level Rise. Science, 265: 228-231.
Warne, A.G. and Stanley, D.J. (1993): Archaeology to refine Holocene subsidence rates along theNile delta margin, Egypt. Geology, 21: 715-718.
Keywords: Egypt, Nile delta, archaeology, sediment core, Holocene, topography©2016. Japan Geoscience Union. All Right Reserved.

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