Kunio Omoto

Nihon University

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Calibrated ¹⁴C Ages of Jomon Sites, NE Japan, and their Significance

Radiocarbon (2010)

Kunio Omoto Kenji Takeishi Shigeru Nishida Jun-ichi Fukui

The traditional archaeological chronology in the Japanese Islands during the Jomon period was essentially based on the relative age given to cord-impressed patterns marked on pottery, as well as the shape of the pottery and the thickness of the cultural layers that were excavated. We aimed to correlate the classical archaeological chronology with calibrated radiocarbon dates, to posit a new chronology for the Jomon period in northeastern Japan. We calibrated 80 accelerator mass spectrometry (AMS) 14 C dates from NE Japan and reconstructed a chronological timetable for Hokkaido and the Tohoku District. We collected 43 samples from 5 shellmounds and 2 archaeological sites on Hokkaido Island and 4 shellmounds in the Tohoku District in order to determine the calibrated age of their sites. ΔR values used on Hokkaido Island and the Tohoku District were between 282 and –158 yr and between ±0 and –40 yr, respectively. The large ΔR value for the eastern part of Hokkaido Island indicates the influence of the Oyashio Current, while an anomalous ΔR value was obtained from northern Hokkaido Island. These figures show larger apparent ΔR values than those from southwest Japan (Nakamura et al. 2007). The calibrated Jomon period in the investigated area was from 2000 to 200 yr younger than the previous chronology. Calibrated 14 C ages of the shellmounds investigated ranged between ∼6000 and 3000 yr, correlating to the Early Jomon and Final Jomon periods as indicated by the former archaeological chronology of Honshu Island.

Chronology

Accelerator mass spectrometry

Absolute dating

10.1017/s0033822200045574

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Citations (11)

Radiocarbon age and geomorphic development of Wakimisaki-beachrock designated as a natural monument by Nagasaki Prefecture

The American Journal of Gastroenterology (2006)

Kunio Omoto Yūshi Itō

10.14866/ajg.2006f.0.10.0

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Citations (3)

14C Age of Conglomeratic Beachrock Developing on Shimaura Island, Northeast of Miyazaki Prefecture

Kikan Chirigaku (2021)

Kunio Omoto Tetsuya Waragai Akiko Ikeda Yoriko Yokoo A Shiomi

宮崎県北東部の島浦島南部の日井の浜では，陸繋砂州の潮間帯に礫岩質ビーチロックが発達している。この形成年代を推定するため，砂礫を固結しているセメント物質5試料と，貝化石3試料を採取し，AMS14C年代測定を行った。また，セメント物質についてICP-MSによる元素分析を行い，その化学成分を確認した。さらにセメント物質の炭素の給源を推定するため，デュアルインレット式の質量分析計によりδ13Cを測定した。その結果，セメント物質から3,271±32，3,219±24，2,917±22，2,752±24，2,512±24 BP，貝化石から3,791±25，3,744±25 BPおよびModern （103.5 pMC）の年代が得られた。一方，セメント物質にもっとも多く含まれていた元素はCaで27.7%（CaCO3換算で69.1%）であり，次いでMgが2.4% （MgCO3に換算して8.2%）であった。また，セメント物質のδ13Cは＋2.9～＋2.0‰であり，炭素の給源が海水であることを示唆する。礫岩質ビーチロックの形成年代は，砂礫を固結したセメント物質の年代の方が異地性の貝化石の年代より正確であると考察される。よって日井の浜のビーチロックは，3,270～3,220 BPころと，2,920～2,510 BPころに形成されたと推定される。

10.5190/tga.73.1_1

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Citations (2)

Examination of ΔR (local marine reservoir correction) Value in the Sea of Okhotsk Coast, Hokkaido

Kikan Chirigaku (2023)

Kunio Omoto Hiroyuki Kitagawa Tsuyoshi HIRAKOCHI

海洋生物化石の14C年代をより一層正確な暦年代に較正するためには,14C年代較正プログラムにΔR(試料採取地点の14C年代の補正値)を入力しなければならない。Omoto et al.(2010)が報告した北海道オホーツク海沿岸のΔR(-158 yr)は,太平洋沿岸や日本海沿岸のΔR(34 yr~345 yr)と乖離している。この結果を踏まえて北海道オホーツク海沿岸のΔRを新たに決定するため,斜里町のオシャマップ川遺跡とトーツル沼1遺跡から木炭と貝化石をペアとする合計4組の試料を収集してAMSによる14C年代測定を行い,Marine20にもとづきΔRを計算した。その結果,オシャマップ川遺跡III層のΔR(1σ)は-94±60 yrとなり,またトーツル沼1遺跡のPit 2から55±46 yrと135±45 yr(平均95±64 yr)のΔRが得られた。新たに決定されたΔRは,かつてトコロ貝塚の試料にもとづき決定された-158 yr(Marine20にもとづき計算すれば-323±42 yr)とは大きく異なる。

10.5190/tga.75.2_78

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Citations (1)

Report of Calibrated 14C Ages and δ13C Analysis of Beachrock Samples Collected from the Yaeyama Islands, Southwestern Japan

Kikan Chirigaku (2014)

Kunio Omoto

八重山諸島の8島26地点から採取した115のビーチロック試料について14C年代測定とδ13Cの測定を行った。この試料に木村ほか（2003）の2試料を加えて較正年代を決定し，八重山諸島のビーチロックの形成年代と，海浜堆積物を膠結した炭酸カルシウムの給源について考察した。その結果は次の通りである。 1）ビーチロックは，およそ5,560～5,260 cal BP（第1期），5,020 cal BP，4,700～4,660 cal BP，4,360～4,050 cal BP，3,810～3,710 cal BP，3,530～500 cal BP，そしてごく最近までの7期にわたり形成された。 2）ビーチロック試料のδ13Cの最大，最小および平均値はそれぞれ9.4‰，－4.95‰ および2.99‰である。また117試料中の80試料（68.4%）のδ13Cは，海洋生物のδ13Cの範囲（+2‰～－2‰）外にある。 3） δ13Cの数値から海浜堆積物を膠結した炭酸カルシウムの給源は，海水のみでなく，海水と淡水の混合水を起源とする可能性を示唆し，また陸水性続成作用による影響を受けた可能性（再結晶）も考えられる。

10.5190/tga.65.207

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Citations (1)

Ages of Isotope Correction for the Holocene Fossil Coral, Fossil Shell and Calcarenite Samples Collected from Nansei Islands, Southwest of Japan

The American Journal of Gastroenterology (2004)

Kunio Omoto

Calcarenite

10.14866/ajg.2004f.0.71.0

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Citations (0)

Formative Age and Rate of Beachrock, Developed on Ohuratabaru Coast, North of Miyako Island, SW Japan

Kikan Chirigaku (2017)

Kunio Omoto Masashi Omata Kiyoshi Ichikawa

Ohuratabaru coast lies in the northern part of Miyako Island, where beachrock develops continu- ously about 400 m in length and 70 m in width. Eight calibrated 14C ages reported previously were used to estimate formative age and rate of beach rock. They suggest that beachrock was formed from inland toward the present strand line between ca. 1,500 cal BP and present time. The average formative rate of beachrock evacuated from age and distance indicated 3～7 cm/y.

10.5190/tga.68.4_302

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Citations (1)

Radiocarbon Ages and Significance for Beachrock Samples Collected from the Eastern Part of Maibahbama, Southeast of Miyako Island

Journal of Geography (Chigaku Zasshi) (2021)

Kunio Omoto

Comprising beachrock, Maibahbama lies southeast of Miyako Island. It is approximately 400 m in length and 3 to 17 m in width. Fossil shell, coral and calcarenite samples were collected from the eastern part of Maibabahbama in order to determine their ages using accelerator mass spectrometry (AMS). 14C age of a Nerita albicilla yielded an age of Modern (100.7 ± 0.3 pMC); however, Tridacna gigas yielded an age of 981 ± 22 yr BP. Coral fragments yielded an age of 1746 ± 23 yr BP, while four calcarenite samples were between 1350 ± 23 and 1567 ± 22 yr BP. The above samples were collected from two outcrops standing 1 m apart and within a 10 cm circle. Five of the seven samples coincided with the estimated ages of past tsunamis within an error range of ±3σ. Consequently, the several samples collected from beachrock at the eastern part of Maibahbama might have been washed ashore by past tsunamis before being cemented. Formation of the eastern part of the beachrock started at 980 yr BP and ended recently. Therefore, they do not coincide with the older ages of other tsunami boulders (Porites sp.) nearby, reported previously.

Outcrop

Calcarenite

10.5026/jgeography.130.99

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Method of Drawing a Precise Contour Map with a Terrestrial Laser Scanner: Example of Mapping Travertine Terraces of the Bora Coast, Southeast Miyako Island, Designated a Natural Monument

Journal of Geography (Chigaku Zasshi) (2017)

Kunio Omoto Kunikazu Tanaka Shigeo Matsuda Kaoru Yokoyama

The travertine terraces of the Bora coast, at the southeastern part of Miyako Island, Okinawa Prefecture have been designated and notified as a new natural monument by the Ministry of Education, Culture, Sports, Science and Technology and Agency for Cultural Affairs. They are distributed in a small area, ca. 70 m (long) × 30 m (wide), and lie between the low-tide level and 6 m a.s.l. Their diameters are between 10 cm (minimum) and 6 m (maximum), while the relative heights among rimstone pools are between 1 cm and 1 m. The terrestrial laser scanner (TLS) technique is an effective method for drawing precise contour maps and expressing complex small-scale topography. In addition, it is cheaper and less time consuming than producing a map with a total station. To express the characteristics of the travertine terraces, precise contour maps are drawn with 2.5 cm and 20 cm contour intervals using a TLS (VZ-400) and software programs. Information is provided for readers who need to draw a precise contour map successfully with TLS and software programs. The principle and application of the terrestrial laser scanning method are described in the text. Large-scale precise contour maps and photographs of travertine terraces are also presented.

Contour line

Christian ministry

Laser Scanning

Geologic map

10.5026/jgeography.126.653

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Citations (0)

Radiocarbon Ages of Organic Materials Collected from Naruko Basin, Miyagi Prefecture.

The Quaternary Research (Daiyonki-Kenkyu) (1993)

Kunio Omoto

10.4116/jaqua.32.227

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Citations (5)