The Quaternary Research /+ 0 p -+1--*,*+, +, AD 3+/,a * * * * +, - + C atooa AD 3+/ AD 3-* 3* BTm Tooa BTm : a I atooa AAD 3+/ : +31, ; +32+ ; Hayakawa, +32/ ; +332 +310 +333 AD 3+/ +310 II,*+, 1 +3,*+, 3,3 * + 3/*,+2+, 2*/* *, 3/*,+2+, 2*/* *- 0-+ 2/*, +/** * /,/ ***+ +*3+ * a Corresponding author : ono@edniigata-u ac jp
318 /+ 0 + Fig + Index mapshowing Towada caldera, Tsugaru Plain and distribution of major archeological sites,* +* m, /,* km, 0* km +* * m / m * / m +310 + AD +*** ++** +310 +33 +,*++ - III +310 m,,+ *43-43 m + C
,*+, +, 319, Fig, Map of the study area - ABC,** + C 0 +310 + C OxCal -4+* + 2 + +0 mm Ramsey, +33/,,**+ + -* IntCal* Reimer et al,,** MAIOT Measuring Actual Immersion Oil Temperature, C +33/ - +* cm 3 J+ J3 20120020/ 203, /4 m*4/ m / +* cm + / cm IV J + + mm, + +2 mm, +2 ++0 mm, ++0 mm AA - +2 ++0 mm BB
320 /+ 0 - AA, Fig - Columnar section (transect of AA ) Localities are shown in Fig, AA J +*,03 J +*,01 BB J+*,1 + J+*,0, J+*,0- J+*,00 AA m / m / m AA BB + - C
,*+, +, 321 BB, Fig Columnar section (transect of BB ) Localities are shown in Fig, Table + + + C Radiocarbon ages from the study area +,4, m -4 m -5,+* yrs BP +5/-* +5+* BC,510*, *4+ *4- m yrs BP +5*** 2,* BC 4 AD +5*** 41 m 4 m +5-** yrs BP AD 0/* 12*,*++ + C A, m, V + +4+ m *4, m / *4- m
322 /+ 0,* cm *4/ m A 42 m /4* m *4+ m + C, +5+2* yrs BP AD 1,* 1*, AD 11* 31* +5,* + mm yrs BP AD 01* 23* A 2* m B, m, *43 m / +/ cm *4+ m A Fig / /, Geological sections at the Jusanmori archaeological site Localities are shown in Fig,
,*+, +, 323 0 C A B C D Gl : FlQtz : HM : Ha, Hb : Ca, Cb : Ta, Tb : BrObs : Bl : Fig 0 Data ofthe section C in thejusanmori archaeological site, (A) Grainsize distribution, (B) mineral composition, (C) shape of glass shards, and (D) refractive index of glass shards Abbreviations are Gl : volcanic glass shards, FlQtz : feldspar and quartz, HM : heavy minerals, Ha, Hb : platy shards, Ca, Cb : intermediate type, Ta, Tb : pumiceous, BrObs : brown glass and obsidian, Bl : blocky shards
324 /+ 0 J + *4+ m 32 B + /4* m C, J3 J+ +5+* yrs BP AD 12* 33* Ca, Cb J3 B +* m / m, J1 Hb J0 J+ *4/ +4- m C Tb / J + Ha, Hb *4- m *40 m - / cm J3 J+ n+43, +4/+1 J3J1 n+432 +4/+* J0 J+ n+4/** J + n+4/+* +4/,* *4, *4- m - / m *4/ *40 m -* cm - 1 *4/ *40 m + A: +* +/ cm, C J+ J 3 : / J + + cm 0 + J0 J+ J1 B : -/ / cm B+ B, B+,* J0 +,/ cm +, cm -* 1* 0 B, B+ / J3 J+ +/,/ cm J3 mm
,*+, +, 325 1 201 20/ 203, Fig 1 Graphic logs of localities 201, 20/ and 203 at the Jusanmori archaeological site Localities are shown in Fig, C: C / +, cm *4/ *41 cm, cm C, B 201 : + 203 : 20/ 203 : + 200 : + 2 - Fig 2 2 Rose diagram showing palaeocurrent
326 /+ 0 A - Allen, +31, +32, + J +, - +32* : Major et al,,***, +33+ : Gran and Montgomery, - 0,**/ J + B+ 1 n+4/+* +4/,* +* B, BTm : +32+ ;,**- ;,*+* BTm + C C Yatsuzuka et al,,*+* ;,*++ AD 3-13-2 +332 AD 3,3 VI,*+* + n+4/** / m BTm + +5,* C yrs BP AD 01* 23* +5+2* yrs BP AD 1,* 1*, AD 3+/ +32+ ; Hayakawa, AD 11* 31* + +5+* yrs BP AD 12* 33* C +32/ ; +332 ;,*** ;,**- / m Tooa 4 41 m +5-** Tooa + yrs BP AD 0/* 12* C,* b,41 cal kyrs BP :,**1 04+ cal kyrs BP :,**- +/4/ cal kyrs BP : Horiuchi et al,,**1,**-
,*+, +, 327 + AD +33+ AD 3+/ 3+/,**3 +333 Newhall and Punongbayan, +330,**- ;,**2 ; Gran et al,,*++ - *4, km Pierson et al, +33, VII Tooa AD 3+/ BTm + C +33+, Tooa AD +***,*++ AD 3+/ +310 / km BTm + *4, *4/ m *4+ *4/ m *4 *41 m +310 1 km + *4+ *4, m *4, m + m +33
328 /+ 0 B volcano Bulletin of Earthquake Research Institute, University of Tokyo, 0*, /*1 /3, : :,+1**2/0 +332 +* B : : +3-**-*2 - *- *1,**3,**- +* ++ + +- Horiuchi, K, Sonoda, S, Matsuzaki, H and Ohyama, +333 M (,**1) Radiocarbon analysis of tree rings from a +/4/ cal kyr BP pyroclastically buried forest : A +*/ xxiiixxiv pilot study Radiocarbon, 3, ++,- ++-,,*** +32, // CD /310+- 3 ROM QaoPOO Allen, JRL ( +31, ) A theoretical and experimental study of climbing ripple cross lamination with a,*+* BTm field application to the Uppsala esker Geografiska ++0-3-/3 Annaler, /- A, +/1 +21,**1 +310 ++0 0/-00-,/ p,**- +33 0***,0, p +*3 +/+ +0/,*++,,,**- +1 p --0 p +32+ /+ /0, /03 +332 Major, J J, Pierson, TC, Dinehart, RL and Costa, BTm LAGUNA JE (,***) Sediment yield following severe volcan- / // 0, ic disturbancea two-decade perspective from +33/ Mount St Helens Geology,,2, 2+32,, +*+ +,- +-- Newhall, CG and Punongbayan, RS (eds) ( +330) Fire Gran, KB and Montgomery, DR (,**/) Spatial and and Mud : Eruptions and lahars of Mount Pinatubo, temporal patterns in fluvial recovery following Philippines ++,0p, Philippine Institute of Volcanology volcanic eruptions : Channel response to basin-wide and Seismology and the University of Wash- sediment loading at Mount Pinatubo, Philippines ington Press Geological Society of America Bulletin, ++1, +3/,++ Gran, KB, Montgomery, DR and Halbur, JC (,*++),*++ +* Long-term post-eruption elevated sediment yields + +*- +++ at Mount Pinatubo, Philippines Geology, -3, -01 +31, -1* ++,,2,-/ Hayakawa, Y ( +32/ ) Pyroclastic geology of Towada Pierson, TC, Janda, R J, Umbal, JV and Daag, AS
,*+, +, 329 ( +33, ) Immediate and long-term hazards from lahars IntCal* terrestrial radiocarbon age calibration * and excess sedimentation in rivers draining Mt,0 cal kyr BP Radiocarbon, 0, +*,3 +*/2 Pinatubo, Philippines -/ p, US Geological Survey,**3 WateroResources Investigations Report, 3, *-3 Ramsey, BC ( +33/ ) Radiocarbon calibration and analysis of stratigraphy : The OxCal Program Radiocarbon, -1,,/ -* : +3,,**2 Ramsey, BC (,**+) Development of the radiocarbon /* * - program OxCal Radiocarbon, -, -// -0- +310 Reimer, P J, Baillie, MGL, Bard, E, Bayliss, A, Beck, 3 1+ 1-/ JW, Bertrand, C JH, Blackwell, PG, Buck, CE, Yatsuzuka, S, Okuno, M, Nakamura, T, Kimura, K, Burr, GS, Cutler, KB, Damon, PE, Edwards, RL, + Setoma, Y and Miyamoto, T (,*+*) C wiggle-matching Fairbanks, RG, Friedrich, M, Guilderson, TP, Hogg, of the BTm tephra, Baitoushan volcano, China AG, Hughen, KA, Kromer, B, McCormac, G, Man- North Korea Radiocarbon, /,, 3--3* ning, S, Ramsey, CB, Reimer, RW, Remmele, S, +310 Southon, JR, Stuiver, M, Talamo, S, Taylor, FW, 2, 31 /+/ van der Plicht, J and Weyhenmeyer, CE (,**)
330 /+ 0 Impact of lahar on sedimentary environmental changes in the central Tsugaru Plain after the AD 3+/ eruption of Towada volcano, northeast Japan Eisuke Ono*, Kyoko S Kataoka*, Masatomo Umitsu* +,a, - and Yasufumi Satoguchi* Drastic changes in the sedimentary environment derived from the Towadaoa tephra (AD 3+/ erupdeposits) occurred during the Heian Period (AD 13 tion of Towada volcano) This indicates that to ++3, ) in the central Tsugaru Plain Observa- pre-eruptive low-energy wetland to floodplain tion of sedimentary facies in trenches of the in the central Tsugaru Plain was inundated by excavated Jusanmori archaeological site, one lahar after the AD 3+/ eruption The Baegdusano of the largest village of the middle Heian Pe- Tomakomai tephra fall (BTm tephra : AD riod (around AD +*** ) in this area, as well as 3-* to 3* ) overlying the lahar deposits implies data from subsurface sediments at,+ sites ob- the termination of the lahar event within dectained by hand auger, have revealed an exten- ades sive distribution of volcaniclastic sands (lahar In the central Tsugaru Plain, many archaeo- abruptly overlying organic-matter rich logical sites appear above the horizon of the (peaty) silt and peat in the area Radiocarbon volcaniclastic sand bed (ie, lahar sediments ages from the peaty silt, mineral compositions, after the 3+/ eruption) This is probably beand shape and refractive index of volcanic cause the extensive sandy plains formed by glass shards show a sudden sedimentary facies lahar events were preferable places to settle for change from peaty silt to volcaniclastic sand in Heian people and eventually caused an increase the early Heian Period The volcaniclastic sand in habitants in the area bed contains a high proportion of glass shards Keywords : Heian Period, Tsugaru Plain, Towadaoa tephra, lahar * + Faculty of Education, Niigata University 2*/* Ikarashi-Nino-cho, Nishi-ku, Niigata 3/*,+2+, Japan *, Research Institute for Natural Hazards and Disaster Recovery, Niigata University 2*/* Ikarashi-Nino-cho, Nishi-ku, Niigata 3/*,+2+, Japan * - * Faculty of Letters, Nara University +/** Misasagi-cho, Nara 0-+ 2/*,, Japan Science Research Department, Lake Biwa Museum +*3+ Oroshimo, Kusatsu, /,/ ***+, Japan * a Corresponding author : ono@edniigata-u ac jp