PROCEEDINGSINDONESIAN PETROLEUMASSOCIATION
ThirdAnnualConvention,June1974. 77
THEGEOLOGYOFTHECENTRALANDSOUTHSUMATRABASI NS G.L.DE COSTER*) BASIN
DESCRIPTION TheCentralandSout hSumat rabasinsare i mport ant
oilproducingareasontheislandof
SumatraintheRepublicofIndonesia(Figs.1
and2).TheyareTertiarystructuraland
depositionalbasinscomposedofaTertiary sedi ment
arysectionlyingonanunconf or mi t y surfaceofpre-Tertiarymet
amorphi cand igneousrocks.Thesearetwoof thethreebasins
locatedonSumatra( t hethirdistheNort h
Sumatrabasin)alignednorthwest-southeast betweentheBarisanMount ai
nstothesouth- westandtheMalaccaandKarimataStraits and
theJavaSeatothenort heast
andeast.Therocksexposedinthebasinsconsistalmost whollyofTertiaryst
rat at houghseveral upliftedblocksi nthebasins(includingthe
TigapuluhandDuabelasmount ai ns) doexpose
pre-Tertiaryrockatthesurface.Therocks exposedi n theBarisan
Mountains arecomposed ofPaleozoicandMesozoicmet amorphi cand
igneousrocksandofyoung Tertiaryt oRecentvolcanics. Analysis
oftheCentral andSouth. Su- matra basins show thatthey hadvery
similar and relatedhistoriesandcoul d beconsidered as one
largebasinwi t hmany troughs and grabens. The Nort hSumat
rabasin,ontheot herhand,appearstohavebeenseparatedfromthe
CentralSumat raareat hroughout mostofits hi st or y
bytheAsahanarchandcanbetreated
asaseparatebasin.ForthisreporttheCentral andSout hSumat
raareaswillbediscussedand described as separatebasins.
TheCentralandSout hSumat rabasins (see Fig.2)areasymmet ri cbasins
boundedonthe southwestbyfaultsandupliftedexposuresof pre-Tert i ary
rocksalongthemount ai n front of theBarisanMountains;.
onthenortheastbythe sedi ment aryordepositionalboundariesofthe
Sundashelf(site-oftheancestralSunda
landmass);tothesouthandeastbythe Lampunghighandbyan
archthatparallels the eastcoastofSumatra;andtothenort hand nort
hwest bytheAsahan archandtheout crops ofpre-Tertiaryrocksnort hwest
ofPekanbaru.Bot hTheAsahanandLampungarcheswere positiveelementst
hroughout muchofTertiary time,separatingtheCentral andSout hSumatra
basinsfromtheadjoiningNort hSumat raand Sundabasins, respect i vel
y. The twoarcheswere coveredbyshaUowmarineseasonl yduring t he
.EarlyandearlyMiddleMiocenetimetoform t emporaryconnect i
onstotheneighboring basins. Thenort heast ern andeastern boundari
es ofthebasinsalongtheSundashelfandthe Lampunghigharedifficultt
odefineprecisely, but areusuallyplacedwherethesedimentary sectionis
less t han1500feet (460meters)thick andcomposedofPlio-Pleistocene
andYounger stratalyingonLowerTert i aryorpre-Tertiary
rocks.Theboundarybet weenthecentraland
southbasinsisalsoindefinitedueto l ackof
majorstructuralfeaturesseparatingthem.This factoris a not he r
argument forconsidering the twoareast obeonebasin rathert han
two.The boundarybetweenthetwobasinsisusually
drawnasanortheast-southwestbandt hrough thenort
hernpartoftheTigapuluhMountains,j oi ni ngtheaxisofabroadarchext
endi ng southwestfromt he Sundalandmasstoa istructurally
complexareain themount ai n front*)P.T. Stanvac Indonesia
Jakarta,Indonesia. The writerwishes to acknowledge his indebtedness
tothemany geologists and geophysicists presently
andfomaerlyassociatedwithP.T.Stanvac Indonesiaformuchofthegeologic
information addinterpretationincorporatedinthispaper.
Informationwasdrawnfreelyfromdiscussions with colleaguesin P.T.S.I.
and fromthe f'des in the Exploration DepartmenLIn addition, he is
grateful to.personnelintheexplorationandgeology departments of
Pertaminaand" of othereomp/mies
operatinginIndonesiafortheircontributions in
generaldiscussionsabouttheregionalgeologyof the Sumatraarea. IPA,
2006 - 3rd Annual Convention Proceedings, 1974Disc
ContentsContentsSearch78 I|IIIIIlSe. i o . g o a 9 1 ~ e i o o oI ,
, I ,0&I4DAMAN o 0 NICOeAR ~*ISLANDS \ XN OR T H ' % C E N T R
A L A NDSOUTH . ' C ' : - ~ - ' ~ S U . A T ~ S l - R U C T U ~
LBASI NS S C A L E I:15, OO0, OOO 0wO3004 5 0 6 0 0 - 1t'50
KtL,DMi~Tf , l ~z 10~o i. . . . . . . . . . . ~ ( " . . . . :,I$
~,C A MB OD I A " ~I ETN AM~ MA L A Y AI10e IN~ o J0 #, 4W,4S E A0
, ; o . , ~ . , ; o .- i oFI G. II NDE X MA P C E N T R A L A
NDSOUT HS U MA T R A B A S I NS79 |! .oo g, , . ~ $. . q# - -
<
