Tectonics of the Scotia Arc, Antarctica: Punta Arenas, Chile to Ushuaia, Argentina January 1-February 1, 1989

234 Pages·2016·56.14 MB·English

Tectonics of the Scotia Are,
Antarctica
Punta Arenas, Chile to Ushuaia, Argentina
January t-February t, t 989
Field Trip Guidebook Tt80
Leader:
Ian ~ D. Dalziel
Associate Leaders:
KrzysztofBirkenmajer Constantino Mpodozis
Victor A. Ramos Michael R. A. Thomson
American Geophysical Union, Washington, D.C.
Copyright 1989 American Geophysical Union
2000 Florida Avenue, N.W., Washington, D.C. 20009
ISBN: 87590-550-1
Printed in the United States of America
COVER: H.M.S. Beagle atthebaseofMonteSanniento,Tierrad:elFuego
(ConradMartens, inFitzRoy, 1839).
TABLE OFCONTENTS
PARTI-GENERALBACKGROUND
1. Introduction.......... 1
BackgroundPublications 2
2. PlateTectonicSetting 4
3. HistoryofIndianHabitationandofExploration,DiscoveryandResearch 9
TheIndians ... 9
ThePioneers 15
TheSurveyors....................................................................................................................... 18
ThePlateTectonicsEra........................................................................................................................... 19
4. TectonicEvolutionoftheScotiaArcRegion 19
GondwanalandFragmentationand Dispersal 19
MarginsoftheSoutllPacificOceanBasin....................................................................................................... 22
LatePaleozoictomid-Cretaceous 22
Mid-CretaceoustoearlyCenozoic............................................................................................................. 22
Eocene 22.
Eoceneto Oligocene 22
OligocenetoMiocene 22
PliocenetoRecent.......................................................................................................................... .. . 22
EvolutionoftheScotiaSeaFloor 23
GeologicEvolutionoftheContinentalAreas 23
EarlyHistory 23
GondwanalandFragm.entation 24
CretaceousandTertiaryOrogenesis 25
Late CenozoicExtension 26
PlatesforSections 1through4 29
PARTII-FIELDTRIPITINERARY
5. Transitto CordilleraDarwinand CanalBeagle 37
PuntaArenasto SenoAlmirantazgo.......... 37
SenoAlmirantazgoto CaIlalBeagle................................................................................................................. 41
6. CordilleraDarwin 42
GeneralGeology 42
BasementComplex 42
CoverRocks 46
IntrusiveRocks 46
StructuralSequenceandGeometry 48
Tectonic Interpretation 49
ComparisonwithNorthAmericaIlMetamorphic Core Complexes 53
Implicationsfor CordilleranOrogenesis 54
PossibleLandingSites.......... 57
7. TransittoBahiaNassau 64
8. TortugaOphioliteComplex(D. ElthonandW. I.Ridley) 65
Introduction 65
Ophiolite Stratigraphy.......... 65
ExtrusiveRocks 66
SheetedDiabaseDikes 67
GabbroicRocks 70
9. PeninsulaHardyofIslaHoste (R.E. Hanson) 71
Introduction .. 71
FieldTripDescription 73
10. TransittoIslasDiegoRam.irez 76
11. IslasDiegoRamirez(T. J. Wilson,R. E. Hanson, andA. M. Grunow) 76
Geographic Setting 76
Geology............................................................................................................................................................. 76
vii
FieldGuide ,.................................................................................................................... 79
12. TransitofDrak.ePassage ,.................................................................................................................... 81
PlatesforSections5tllrough 12.......... 84
13. ElephantIslandGroup(I. W. D. Dalziel,A. M.Grunow, andR. A. J. Trouw) 95
IntroductionandTectonicSetting 95
Litllology 3I1dMetam.oIphism 101
StructuralandMetam.oIphicEvolution 101
Tectonic InteIpretation 104
PossibleLandingSites 106
14. Transitto KingGeorgeIsland 113
15. KingGeorgeIsland (K. Birkenmajer) 114
TectonicFram.ework 114
RockComplexesand Successions 117
Field ObselVationSites.. 120
16. TransitofBr3l1sfieldStrait 127
17. TrinityPeninsula3I1dJam.esRossIslandArea(M.R. A.Thomson) 127
ArcRocks 128
BasinFill........................................................................................................................................................... 132
Alkaline Volcanism 133
Structureand Originoftl1eLarsenBasin 133
18. TransitofSoutheasternBransfieldStrait,GerlacheStraitandNeumeyerCh3l1nel 137
19. AnversIslandArea 137
20. TransitofSouthernBransfieldStrait..................................................................................................................... 146
21. DeceptionIsland(J. L. Smellie) 146
Tectonic Setting 147
SummaryofVolcanicEvolution 147
DescriptionofOutcrops illustratingVolcanicEvolution 148
22. LivingstonIsland 149
Miers BluffFonn.ation 149
PossibleLandingSites 157
23. SmithIsland(A. M. Grunow,I. W. D. Dalziel, andR. A. J. Trouw) 157
Introduction 157
Structural3I1dMetamoIphicEvolution 157
Tectonic Interpretation 164
PossibleLandingSites 165
24. TransitofSouthwesternDrakePassage 165
25. EasternTierradelFuego andIsladelosEstados(I. W. D. DalzielandV. A. Ram.os) 168
Introduction 168
Regional Geology 168
Structure.................................. 174
PossibleLandingSites 175
PARTIII-WRAPUP
26. FutureResearch: Problems andPotential............................................................................................................. 179
27. Acknowledgements 179
28. References 181
PlatesforSections 13tllrough25 192
viii
ACKNOWLEDGMENTS
Leader:
IanW. D.Dalziel
InstituteforGeophysics
UniversityofTexasatAustin
8701MopacBoulevard
Austin,Texas 78759-8345
U.S.A.
AssociateLeaders:
KrzysztofBirkenmajer ConstantinoMpodozis
InstituteofGeologicalSciences SelVicioNacionaldeGeologiayMinerfa
PolishAcademyofSciences SantaMaria0104
ul. Senacka3 Providencia
31-002Krakow SantiagodeCHILE
POLAND
MichaelR. A.Thomson
VictorA.Ramos BritishAntarcticSurvey
SelVicioGeologicoNacional NaturalEnvironmentResearchCouncil
Av. SantaFe 1548 HighCross
(1060)BuenosAires MadingleyRoad
ARGENTINA CambridgeCB3OET
UNITEDKINGDOM
FieldtripsupportedbyDivisionofPolarPrograms,NationalScienceFoundation,Washington,D. C., U~S.A. (PeterE.
Wilkniss,DivisionDirector); alsosponsoredbytheWorkingGroupforGeologyandtheGroupofSpecialistsonthe
StructureandEvolutionoftheAntarcticLithosphere,ScientificCommitteeonAntarcticResearch,InternationalCouncilof
ScientificUnions.
GuidebookbyIanW. D.Dalzielwithcontributionsby:
TortugaOphioliteComplex-
DonElthon(UniversityofHouston)andW. IanRidley(U.S. GeologicalSurvey)
PeninsulaHardy-
RichardE.IIanson(TexasChristianUniversity)
IslasDiegoRamirez-
Terry1. Wilson(OhioStateUniversity),RichardE. Hanson(TexasChristianUniversity), andAnneM. Grunow
(ColumbiaUniversity)
ElephantIslandGroup
IanW. D. Dalziel(UniversityofTexas), AnneM. Grunow(ColumbiaUniversity),andRudolphA.J. Trouw
(UniversidadeFederaldoRiodeJaneiro)
KingGeorgeIsland-
KrzysztofBirkenmajer(polishAcademyofSciences)
TrinityPeninsulaandJamesRossIslandArea-
MichaelR. A.Thomson(BritishAntarcticSUlVey)
DeceptionIsland-
JohnL.Smellie(BritishAntarcticSUlVey)
SmithIsland
AnneM. Glunow(ColumbiaUniversity),IanW.D. Dalziel(UniversityofTexas),andRudolphA. J. Trouw
(UniversidadeFederaldoRiodeJaneiro)
IsladelosEstados andEasternTierradelFuego(Argentina)
IanW. D. Dalziel(UniversityofTexas)andVictorA.Ramos(ServicioGeologicoNacionalandUniversidadde
BuenosAires)
ix
PARTI·GENERALBACKGROUND outstanding laboratory for the study oftectonic processes
suchascordilleranorogenesis,ridgecrest-trenchinteraction,
andtheupliftofsubductioncomplexes.
1. INTRODUCTION TheScotiaArcregionhasplayedaroleinNorthAmerican
history since Sir Francis Drake followed in Ferdinand
The ScotiaRidge is the east-closing arcuate submarine Magellan'swakethroughtheEstrechodeMagallanes(Strait
topographic high linking the Andean Cordillera of South ofMagellan)enroutetoCaliforniaduringhiscircumnaviga
America to the Antarctic Peninsula (Fig. 1.1). The ridge tionoftheglobein1577-1579. Drakewasblownoffcourse
emergesfromtheseatofonnsmallbutruggedislands: South to thesoutheastaftertransitingtheEstrecho deMagallanes
GeorgiaontheNorthScotiaRidge,andtheSouthOrkneyand from AtlantictoPacific. There,atsomestilldisputedpoint
SouthShetlandIslandsontheSouthScotiaRidge(Figs. 1.2 near Cabo de Homos (Cape Horn) at about 55°30'S, he
and2.1;Pl. 1.1). AllofthesearedisplacedpartsoftheSouth observedthewatersofthe"AtlantickeOceanandtheSouth
Americancontinent(SouthGeorgia)ortheAntarcticPenin Sea,meeteinamostlargeandfreescope"(Morison, 1974).
sula(SouthOrkneyandSouthShetlandIslands). TheSouth Drake'spassage,moreexposedbutconsequentlywithmore
SandwichIslandsthatcloseoffthe ScotiaRidgeintheeast searoomforsailingvesselsthantheEstrechodeMagallanes,
constitute one of the least mature intraoceanic island arc providedthecriticalsearoute aroundSouthAmerica. Dis
systemsoftheworld. Eightoftheelevenislandsinthearcare coveryoftheAntarcticPeninsulasouthofDrakePassageby
presentlyvolcanicallyactive (pI. 1.2). American,British,andImperialRussianexpeditionsdidnot
Thesixtiethparallelsouthpassesthroughthearcimmedi followuntiltheseconddecadeofthe 19thcentury,butsince
atelysouthoftheSouthSandwichIslandsandtothenorthof then the United States has been continually involved in
theSouthScotiaRidge. ThustheSouthOrkneyIslands,the explorationand discoveryatsea, onland, inthe air, and in
South Shetland Islands and the Antarctic Peninsula lie in spacethroughouttheScotiaArc region.
territory covered bythe AntarcticTreaty. Southern South Asthereisnocountryto"host"anInternationalGeologi
AmericaisArgentineandChileanterritory. SouthGeorgia cal Congress in Antarctica, it seemed appropriate on the
.and the South Sandwich Islands are administered by the occasion ofthe 28th International Geological Congress in
UnitedKingdomandclaimedbyArgentina. Inthisgeologi Washington,D.C.,thefirsthostedbytheUnitedStatesfor53
cal guidebook Spanishlanguage place names are used for years,toincludeafieldtriptoAntarcticaamongthoseoffered
SouthAmericaandEnglishlanguageplacenamesforSouth atthe beginningofthe eraof"earthsystem science." The
Georgia,theSouthSandwichIslands,theSouthOrkneyand DivisionofPolarProgramsoftheNationalScienceFounda
South Shetland islands, and the Antarctic Peninsula. It tion agreed to make available Antarctic Research Vessel
shouldbenotedthattheseEnglish-languageplacenamesare PolarDukeinordertofosterknowledgeandunderstanding
notuniversallyaccepted. Forexample,theAntarcticPenin ofAntarcticearthscienceinaglobalframeworkamongthe
sulaisTierraSanMartinintheArgentineliteratureandTierra internationalgeologicalcommunityandtopermitconstruc
O'Higgins in Chilean publications. Additional complica tive criticism ofworkundertakeninthe ScotiaArc region.
tions ariseinstratigraphicnomenclature, and areproliferat Appreciating, however, that several other countries have
ingwithanincreasingnumberofcountriesactiveinthearea. active geologic research programs there, it was decided to
The Scotia Ridge was named after S.Y. Scotia of the seek the co-sponsorship of the Scientific Committee on
ScottishNationalAntarcticExpedition(1902-1904). Itwas AntarcticResearchoftheInternationalCouncilofScientific
this expedition, led by W. S. Bruce, that found the first Unions(S.C.A.R.). Thiswasgrantedthroughthe S.C.A.R.
evidence of a submarine ridge joining the Andes and the Working Group on Geology and the S.C.A.R. Group of
AntarcticPeninsula(RudmoseBrownetal., 1906),although Specialists onthe Structure and Evolutionofthe Antarctic
earthscientistshadsuggestedafterthefirstAntarcticdiscov Lithosphere. Theleadersoftheearthsciencecommunitiesin
eriesintheearly 1800'sthatthe "Antarctandes" are acon bothArgentinaandChilegenerouslyagreedtoendorsevisits
tinuationoftheSouthAmericanAndeanCordillera(Barrow, toremotesouthernpartsoftheircountries. Thegovernments
1831). The entire feature from the eastward CUlVe ofthe ofbothcountriesgrantedpermissionforportcallsandland
AndesinTierradelFuego,throughtheScotiaRidge,tothe ings. Withoutsuchunderstandingthefieldtripcouldnotbe
recurvedAntarcticPeninsulaisnowknownastheScotiaArc. scientificallycomplete. Finally,theinvolvementofAssoci
ThenameSouthSandwichArcisconfinedtothevolcanically ate Leaders from Argentina, Chile, Poland, and the United
activearcofislandsattheeasternextremityoftheScotiaArc, Kingdom,andcontributionstothisGuidebookfromthirteen
afeaturecomparabletotheLesserAntillesvolcanicarcthat scientistsinthosecountriesplusBrazilandtheUnitedStates,
closesoffthe CaribbeanArcintheeast. The ScotiaArcis speaks well of international scientific cooperation in the
nowknowntobeacomplexsegmentoftheSouthAmerican region.
Antarcticplateboundary. Itislocatedinacriticalposition Afieldtriptooneofthemostremoteareasonearth,and
with regard to the Proto-Pacific (panthalassic) margin of oneaccessibleonlybysea,cannotbedescribedinthesame
Gond"wanaland, the fragmentation of Gondwanaland and mannerasonetoanareacriss-crossedbyfederal, state,and
development ofthe young southern ocean basins, and the local highways. Nonetheless, this Guidebook attempts to
historyofthecircum-polarcurrentandofAntarcticbottom givethesametypeofbackgroundinformation, enroutede
water flow. Moreover, the region ofthe Scotia Arc is an scriptions ofthe geology transited, and generallocalityde-
IndianOcean
SouthAtlantic
Ocean
PacificOcean
FIGURE 1.1 Locationofthe ScotiaArcinrelationto SouthAmerica and AntarcticaonGEOSAT"deflectionofthe
vertical" fabric map of the Antarctic plate and adjoining areas. ....r- - Ocean ridges and transforms;
) , , " - Rifted margins of Antarctica; " ... - Subduction zones of Antarctica; " " , ,
I -
Inferred normal fault; - - - - Boundary of crustal block; AP - Antarctic Peninsula; BSB - Byrd Subglacial
Basin; BST - Bentley SubglacialTrench; EWM - Ellsworth-Whitmore Mountains; GSM - Gamburstev Subglacial
Mountains; H - Haag Nuilataks; MBL - Marie Byrd Land; RNIS - Ronne Ice Shelf; ROIS - Ross Ice Shelf; TI
ThurstonIsland. (GEOSATaltimetrydataprocessedbyD.T. Sandwell,InstituteforGeophysics,UniversityofTexas
atAustin; seeSandwellandMcAdoo,inpress.)
scripuons,asthoseintheotherguidebooksforfieldtripscon BackgroundPublications
nected withthe 28thInternationalGeological Congress. It
must, however, be rather general in its approach because A standard reference list is provided at the end ofthis
specificlocalitiesmaybeinaccessibleonagivendaybecause Guidebook. Itassumesthatthereaderhasavailableacopyof
ofweather,ice, andseaconditions. the colored Tectonic Map ofthe Scotia Arc at a scale of
2
~ FALKLAND ISLANDS
~~
ISLAS MALVINAS
K £
R A
D
55°
FIGURE 1.2 PhysiographicmapofDrakePassageareawithplannedcruisetrackforFieldTripT180of28th
InternationalGeologicalCongress(AntarcticResearchVesselPolarDuke).
3
»
Scotia
.."
:c
Drake--....·
South SCotia 11.
•• .. Idge
SOl ~
Shetland
ANT ANT
Limit of B.A.S. (Mise) 3 Polar Stereographie
Proj~etion 20mm/year
(l/J 0 150 300 450 600 ~
30'=0W=- ~~~ U OOS 0° ' , , , , 600S
0 km
FIGURE 2.1 Plate tectonic setting ofthe Scotia Arc from Tectonic Map ofthe Scotia Arc (1:3,000,000, British
AntarcticSurvey;BASMise3, 1985). APR-AfricanPlate;ANT-AntarcticPlate;SAM-SouthAmericanPlate;SO
SouthGeorgia;SOl-SouthOkneyIslands; SSI-SouthSandwichIslands. Arrowsshowrelativeplatemotion(lengthis
proportionaltorelativevelocity). NOTE: BoxoutlinesareaofTectonicMapoftheScotiaArc.
1:3,000,000thatwasjointlyproduced bythe United States Carta Geo16gica de Chile, Hoja Isla Hoste e Islas
andtheUnitedKingdomandpublishedbytheBritishAntarc Adjacentes, Chile, 1:250,000, Servicio Nacional de
ticSurvey,CambridgeasMapBAS(Misc.)3. Itisavailable GeologiayMinerfa,Mapa65,Santiago,Chile, 1985
insinglesheetsthroughEdwardStanfordLtd., 12-14Long
Acre,LondonWC2E9LP,U.K.ata1988priceof$US15.00 Geological Map of Segments of Gondwana,
pluspostageandhandlingandisbestpurchasedfrom over 1:10,000,000, American Association of Petroleum
seasbyaletterauthorizinguseofaVISAcardorequivalent. Geologists,Tulsa, Oklahoma, U.S.A., 1988
Adescriptionofthemapisbeingpublished:
Copiesofallfive mapslistedwillbesuppliedtopartici
Barker,P. F., Dalziel,I. W. D., and Storey, B. C., in pantsinFieldTripT180ofthe28thInternationalGeological
press,TectonicDevelopmentoftheScotiaArcRegion, Congress.
InTingey,R.(Ed.),TheGeologyofAntarctica,Oxford
UniversityPress, 1989. 2. PLATETECTONIC SETTING
Availabilityofnauticalchartsisassumedforlocalplace The present-day plate tectonic setting ofthe Scotia Arc
name·s. regionisshownonFigure2.1togetherwiththeboundariesof
theTectonicMapoftheScotiaArc. Thesettingisdescribed
Othergeologicmapscoveringtheregionare: indetailinBarkeretale (inpress) andwillbeoutlinedonly
brieflyhere.
CartaGeol6gicadeChile,GeologiadelaRegi6nalSur East-west relative motion ofthe South American plate
deCanalBeagle,Chile, 1:500,000,InstitutodeInves (SAM)andtheAntarcticplate(ANT)attheslowrateof20
tigacionesGeol6gicas,Chile,Mapa36,Santiago,Chile, 24mm/yr(Chase, 1978;MinsterandJordan, 1978)istaken
1978 upentirelyinawestwardfacing subductionzonealongthe
westernmarginofSouthAmericasouthofthe ChileRise
BritishAntarcticTerritory GeologicalMap, Sheet2, ChileTrenchtriplejunctionatapproximately46°S. Tothe
North Graham Land and South Shetlands Islands, south of 52°8, as the Andean Cordillera swings eastward
1:500,000 (BAS 5000 Sheet 2 Edition 1), British throughthePatagonianorocline(Carey,1955)intotheNorth
AntarcticSurvey, Cambridge,UK, 1979 Scotia Ridge, an increasing component ofeast-west strike
4