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I..ANI)FOR5・ISANDMANGROVEHABITATINT11ESATUNLOXVLAND,SOUTIIEllNTHAILAND
MasatomoUMITSU゛,PaiboonPRAMOJANEE大・,AkioOHIRA角・大,KumikoKAVVASE゛andJingFANG゛
゛DepartmentofGeo琴巾尚垂聯自警匹oyauniversity9・IAPAN゛゛SchoolofMarineandCoastalResourceManagementTechnology,
iValailakuniversitv,THAILAND~゙ SchoolofEduc・ltion,M珍azakiuniversity
lntroduction
Them。grovev雨雲tatedshorelineshad
widelydevelopedinthesouthwesl:empaftof
theMalayPenisula.lnthelatterhalfofthe
twentiethcentury,mostmangovevegetation
insouthemThailand,however,was(lestroyed
byhumana(;tivities(Aksomkaoeand
Paphavatist,1993),andwdlprel;erved
mangrovefol`estscanbeseenonlyinafew
limitedareas。
Thisstudyaimsatexllminingthelandforms
andsedimentsofanestuarinelowlandin
l’elationtothemangrovehabitat,andalso
discul;sestheefTectofthefilturesealevelrise
causedbythe11reenhouse{1111ecttothe
mangrovedistributionofthestudyarea。
ThestudyareaistheSatunlowlandinthe
southw6tempartoftheThajlandwherethe
rnangoveve筝tatlonlspl ‘゙:;servedlna
rdativelybettercondition.
Regionalsettings
TheSatunlowlandlocatesinthe
southwel;tti‘npartof゙ IS4alaype111stlla,andis
sulToundedbyrelativelylowmountainsandhinswithheightofseveralhundredmeters.
Thelowland,about25kmfromnorthto
southand10-lj5knln・omeasttowest,faces
totheStral小tofN,1111acca,andsomeisolated
limestonehinscanbeseeninthelowland。
Theheightofthelowlandisabout20min
thenorth,5-8minthecentralpart,lower
than2-3minthesouthempart,respectively・
Mostl;otlthempartofthelowlandislower
thanhi小tidelevel,andis皿)veredwith
mangovevel芦itation.Tidalran誤()f` thisarea
basedonour()bservlltionsinDecember1996
andinSeptember1997wasapproximately2
to3meters.
FigJMapshowingtheSatunlowland.
Nlethods
Geomorpholoがcalandgological
investiptionhavebeendoneinlate1996and
middle1997.Aほldfomlclassifical:ionmap
wasdrawnusing1:40,000scaleaerialphotos.
Toclarifythelandformsandge()k)gical
121jaturesoftheregjon,theauthorsdidneld
research皿d(;ollectedsomel;anlplesusinga
handauga’.Somesampleswere∞hctedfor
- 1 5 5 -
radiocarbondatingalldforbothchemicajand
paleontologicalanalyses.TheboringsitesinthelowlandareinandaroundSatunurban
area,andinseveralspotsalongtheroad
number4183toFerryport,
LandformsoftheSatunlowland
Theelevationofg’aterpartofsouthem
Satunlowlandisbetweenthenleantidelevel
andhi小ti(lelevel,andthereがoniscovered
withtidewaterduring
l:heh肺tie.Thi,;1・(,gion1台台轟面映(:lasatidal
plain.IUversastheKhlongThaChin(ChinRiver),KhlongPhrao(PhraoRiver),Khlong
l3slBang(Ban1BangRiver)nowinthesouthempartofthelowland,andmanytidal
cl‘eeksdeveloponthetidalplain.Amongthe
tidal(;1-eeks,therearesomelargcreeksasthe
KhlongTaMiang(TaMiajngCreek)witha
widthofseveralhundredmeters.Themouth
oftheseriversformsalargee5;tuary,andit
extendstotheinlandapproximately2,5and
withthenlaximumwidthis2.0km.Tidalnats
developalongthemouthoftheel;ttlaryinthe
levelbetweenrlleantideandlowtide.
Mangrovefol‘estsdeveloponthegeaterpart
oftheuppertidalplain,butmuddysediments
areexposedinthetidalnat.
0ntheotherha.nd,thedensityofl;treamnetworkislowinthenorthemhalfofthe
lowland。
Riverscannotbeseeninthecentraland
northemlowlandexcepttheKhlongW皿gPra
(Wa.n11PraRiver)anditり)ranchesandKhlongBamBag(BamBangll,iver).Thesel`ivers
(nssectthesurface()f゙ thelowland,andform
nalTowvalleyplains.Relativehei小ts
betweenthe陶成lceofthelowlandandthe
vaneyplainsare3-5meters。
Sincethee21stemmountainsandsmallhills
inthe(;entrallowlandareconsistedof
limestone,theslopesofthemountainsand
hinssu汀oundedbythelowlandarevery
l;teep.Lowandgentleslopesandrelatively
natsurfaceswiththeh面映tofabout20-30m
developalongthefootofmountainsandhills
inthew6temmarljnofthelowland.The
mrfacesedimentsofthere画onafeoxidizedin
deepreddishbrown()()1()r、anditis
remarkablydUfflrentfiomthesedimentsof
thelowland.
I)kistocenesediments
uppersedimentsofnorthemhalfofthe
lowlandisremarkablyd汀ferentfyomthoseof
thesouthemh毒曇Theboundaryofthetwo
男旱onsisalmostalongtheeast-westline
acl’()sstheSatunurbanarea。
lnnorthempart(:)f` thelowland,thel;urface
sedimentsconsistofthegaywhiteand
occsiona11’e(ldishmottledsiltys飢dorsa,ndy
silt.Thissedimentsarel’elativelyhafdand
compact,alsoseenintheoutcropsnearthe
airportwhichlocates2kmnorthofSatun
urbanarea。Thel;url:11cesedimentsofthearea
aroundBanThaChinwhichlocatesnorthof
theKhaoWangMan(Mt.WajngMa,n)arethe
same.Sincethesedimentsafenotdeeply
weatheredincomparisonwiththereddishweatheredsedimentsinthesu汀oundingrφon
ofthelowland,itseemstobefk)rmedinthelatePleisl:()cene。
Thesul-IF11ceofthisPlei山)cenesediments
l)ecomeslowerandisc()veredwithrecent
muddysedimentstowardstheso山:hempart
()fthelowland.The(lepthsofthePleil;tocene
srfaceare0.5-1。0minandaroundthe(:;entral
partofSatunurbanarea,2minthe釦u幽emmarginofSatunurbanareawhichlocates10
kmfromthecoast,andabout5matthesite
about5kmn’omthecoast.Thel;urfllceis
lowerthan7mintheregionnearthecoast。
ltisclearthatthe5;ulfaceofthis
Pleil;1:ocenesedimentsbecomedeepertowards
thesouth,anditfbrmsalow筝ntlel;urfllcein
thenorthempartofthelowland.Asthe
gradientofthisPleist()cenesu吋a£eisl;teeperthanthetidalplainofthelsouthemlowland,
thePleis;1:()cenel;urfaceisconsideredtobe
fk)rmedinthelatePleistoceneorthelast
glacialperiodunderthelowersealevel.
Holocenesedimentsandtheirage
ThesedimentswhichcoverthePleistocene
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Mostofthesedimentsinthesouthempart
oftheSatuncoastallowlandconsistofmuddy
sedimentswithpeatlayerintheupper卜1.5
m.Themuddysedimentsaregreengayor
blueぎaycolor,anditsu留eststhatthe
sedlmentsaremanneongln。
Apeatlayerinthemuddysedimentsatthe
siteof961130-4canbeseeninthedepthof
3.10-330m,A筝ofthepeatis6640±90
yrBP(NUTA-5161).Thisshowsthatthe
l)eatlayerwaslFormedintheculminationoftheHolocenetrajnsgression.Ageofthepeaty
materialintheupperpartofthemuddy
sedimentsnearBanKaianBatualthesiteof!;)61201-lis5710±100yrBP(NUTA-5159).
Thisalsoshowstheal尹ofth(5culminationof
theHolocenetransgression。
ConcentrationofwoodylFyallmentscanbe
seenatthedepthsof5.06-5.78mand6」8-
6,94mofthesiteat970922-1,3kmfromthe
coastline.Sedimentsinbetweenandoverthe
woodyl:hgmentsaresandorsandymud.
A聊邑ofthewoodfragmentsare950±130
yrBPatthetophorizonand1270±200yrBPatthebottomhorizon,resp警謐vely.These
al尹5;sugl尹stthatthewoodyf` ragmentsarenot
thet)a5;alpeatbutthecon(こ(うntrationofdrifted
m2 -
1
0
1
2
3
4
5
6
961130-1
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- - -
Peatymud
W -
Silt- - -
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;Sandysilt
Marineclay
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Silt
W - 〃 〃 ・ - - 〃 - J I I - 〃 -
Siltyclay
リIS4-
Woodfragments
970922-1
Peat-Peatymud- - - W - - 皿 - -
M t x j
970923-1
Marinemud
Sandysilt
woodlfi’agmentsalongsandspitorbarwhich
extendedfi・omthewest.
Landfi)rmsandMangrovehabitat
Asmentionedabove,thelandlFormsofthe
Satunlowlajldarenotasimplegomorphicl;tlrfacebuttheml‘facesofPleistoceneand
lateHolocene.ltisfairlyhardtodistingμish
theboundafyoftwos;ul・facesinthefield,but
itispossibletotracetheboundaryfiomthe
detailanalysisofaerialphotos.These
boundariescanbeseennotonlyalongthe
KhlongWangPrabutalsoalongtheKhlong
ThaChin(ThaChinRiver)andtheKhlong
KhanChin(KhanChinRiver).Thesel’iversdissectedthePleil;tocenel;tlrfacevery
shallowlyandlデk:)rmednarrowvalleyl)lains。
UppersoftsedimentsonthePleil;tocene
sedimentsnearthecentralpartofSatunurban
areaareverythinandrnainlyconsistofsandy
sediments.Thisl;t111Fststhatmangrove
,reli,tationhaven’tc,)veredtheregionsince
themiddleHolocenewhenthemarinearea
e)cpandedaccordingtothepostjacial
trarls;gresslon‥
Mangrovevegetationd(うvelopsnorthof
KhaoWangMan(Mt.WangMan)which
l,:)cateseastofSatunurbanarea.The
%11304970922-2961201-2970923-2
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心
手.3Geological(;rosssectionoftheSatunlowland斤omsouthtonorth.
-158-
0 lkm
1‘4uddyPeat
PLEIST(XこENE
Marinemud
A
CoarseSand
〃 〃 〃 〃
IFりeistocenel;urfllce,however,(ievelopsjust
northofthel)resentmaJlgoveforest.This
rll,:濯lsthatthen71angr(:)veforest❼ヲ` theareain
themiddleHolocenee7q)andedalmosttothesouthemendofthePleistocenel;ulfllce。
Mangrovevegtationneaftheeasternpart
ofSatunurbanareainthemiddleHolocene
a15;oexpaJldedtothel;outhemendofthe
l)leistoceneliul‘face,Thepresentmangrove
limitoftheareaisalsoverydosetothe
southemPleistocenelimit.ltisaboutlkm
southfi・omthePleistocenestldace。
SouthemmostpartLoftheSatunurbanarea,
however,isnotcoveredwithma.ngrove
R)rests,andtheareaissubm琴声dbynood
tideinthetimeofhi小tide.Thismeansthat
thep妻皿ntlimitofthe111angrovehabitatin
theareaisnotthenaturalconditionbutthe
conditioncontrolledbythehumaJlactivity・
Furtllermore,thedistancebetweenthe
sollthemendofthePleisl:(:)cenesl血ceand
thenortllemendofthepresentMangrovefol’estsalongtheKhlongPharao(thePhafao
River),justeastofSatunurbanareaisonlylkm.ThislsuglgeststhemiddleHolocene
l‘11angrovelimitwasnotarn’omthepresent
mangrovelimit。
Thereisnodetailrecordofthemiddle
HolocenesealevelintheSatun鸚皐on.Evenif
thesealevelinthemiddleHolocenewas
hi小ertha,nthepl‘esentsealevel,thelimitof
mangrovevegiitalionatthattimewasnotso
dほerent斤omthatofthepresent,becausethe
southemlimitofthePleistocenel;urfhceis
veryclosetothepresentmangrov{31imit.
Concludingl‘{lmarks
Landforms()ftheSatunlowland(;onsistof
Pleil;toceneaJldlateHolocenelsurfllces.The
Holocenesurfactl(;onsistofthelateHolocene
sedimentswhichdepositedinandafterthe
Holocenetransgession.Southempartofthe
lowlandisclassinedasatidalplain,andthe
levelofthetidalplainisbetweenhi小tideandlowtide.Presentinangrovev響蓼tation
developsonthetida11)lain.lnthemiddleor
lateHolocene,nlangoveforestdeveloped
alongtheexl)andedinletoftheSatunbayand
southemlimitofthePkistocenesurface.
DistancebetweenthenorthernlimitofmangroveforestinthemiddleHoloceneand
thatofthepresentoneislessthan2kmin
rnaxlmum。ICPP(1995)estimatesthesealevelrise
unti12100ADtobeabout50cmasthemean
valueandaboutlmasthenlaximumvalue.Thesevaluesaren’thi小erthaJlthemiddle
HolocenesealevelintheMalaypeninsula
参蓼()nr(・portedbyl;insakl(1992).Andsince
幽ePleilsll(:)c{311esurface()nheSatunlowlandisrelativelysteeperandhi小erthanthe
Holocenelsul’face,southemmostpartofthe
Pleil;tocenesurfllcewinnotbecoveredbythe
expandedinletcausedbythesealevelrise,
Thel-efbre,evenifitisassumedthatthesea
leve11-{iachestotheestimatedvaluein2100
ADunderthepredictedsea-levelrise‘こaused
bythegeenhouseeffect,nlanぎoveR)rest
willnotexpandfurthernorthofthelimitof
l:heMiddleHolocenemangroveforest.
Acknowledgment
Wewouldliketoexpressourthanksto
ProflT、Kawana、Mr.K.lchikawa、Mr.J.
TsuchiyaandMr.T.Takaifortheirfield
assistanceofaugringWealsoexpressour
l:hankstoDr.CharlchalTanavud(Princeof
Son福轟un沁・i・rsty、’Trhail飢d)forhiskindhelptoourl゙ elserch.
References
Aks;ornkaoe,S.andPaphavatist,Nittharatana
(1993)回忌ctofsealevelriseontheM皿groveEcosysteminThaila.nd,Malaysia,n
JoumalofTropicalGeography,::!4,29-34.
1PCC(1996)Climate(こhange1995.-The
5;cienceofClimateCange-.Contributionof
WGltotheSecondAssesmentReportofthe
ln奉啓vemlentalPanelonClimateChanl尹,
(2111nbridgeUrl沁ersityPrel;s,572P.
5;irl・;akl,S.0!;)92)IEE;vid・・rlceof(:ju・l.temarysealevelchangsinthec(:)astalareasof’I` hailand:
areview.JoumalofSoutheastAsillnEarth
!;ciences,7,23-37.
- 1 5 9 -
海 津 正 倫 論 文 ・ 研 究 報 告 ・ 学 会 発 表 な ど
(論文等)
海津正倫(1997)デルタ地形と海水準変動.月刊地球j.9J5()-556UI・nitsu,M.(1997)Landformsandf’1()odsintheGangesdeltaandcoastallowlandofBanllhldesh.MarineG{3o(le5;y,20,77-87.
Urnitsu,M,PramojaneeP.,0hira,A.,Kawase,K.andFang,J.(1998)I.,andformsand
MangroveHabital:intheSatunLowlalld,SollthernThailand.名古屋大学加速器質量分
析計業績報告(IX),(inpress)Urrlitsu,M.(1998)Holocene,;edimentaryenヽ /ironmentalchangeofcoasrE1日wlElndsin
,lapan.名古屋大学加速器質量分析計業績報告(IX),(inpress)
(学会発表等)海津正倫・川瀬久美子・C.Woodroffe(1997)「オーストラリア5i;110,1111aven低地における堆積物の年代と地形形成.1997年度名古屋大学タンデトロン加速器質量分析計シン ポ ジ ウム 「 最 新 型 タ ン デ ト ロ ン 加 速 器 質 量 分 析 計 に よる 高 精 度 ・ 高 分 解 能 1 4 C 年 代測 定 の 利 用 分 野 ・ 方 法 の 開 拓 」 ( 名 古 屋 大 学 )
Urnitsu,M.(1997)DevcうI()pmentandEnvironmentalChangesoftheJapaneseD,:・ltas.REKIHAKUlntel・1・lationaISymposium:Terl・{:5striaIEnv汁onmentalChangesandNaturalDisElsters(luringtheLa・;t10,000Years.(国立歴史民俗博物館)
海津正倫(1997)沖積低地の古環境変遷と人間活動.タンデトロン加速器年代測定装置の 学 際 利 用 と そ の 地 球 環 境 解 析 へ の 応 用 . 名 古 屋 大 学 年 代 測 定 試 料 研 究 セ ン タ ー シンポジウム.(名古屋大学)
海津正倫(1997)完新世における環境変化と熱帯デルタの地形変化.地球惑星科学関連学 会 合 同 大 会 シ ン ポ ジ ウム , 地 球 規 模 変 動 に 対 す る 熱 帯 海 岸 環 境 の 応 答 と 対 応 戦 略 .(名古屋大学)
海津正倫( ‘ 1罷賜)デルタ海岸の地形変化.IGCPシンポジウム「最近地質時代の地球環境」.(神戸大学)
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