Tectonic, Climatic, and Cryospheric Evolution of the Antarctic Peninsula

214 Pages·2011·21.9 MB·English

Tectonic, Climatic,
and
Cryospheric Evolution
of the
Antarctic Peninsula
John B. Anderson and Julia S. Wellner
Editors
Published under the aegis of the AGU Books Board
Kenneth R. Minschwaner, Chair; Gray E. Bebout, Kenneth H. Brink, Jiasong Fang, Ralf R. Haese,
Yonggang Liu, W. Berry Lyons, Laurent Montési, Nancy N. Rabalais, Todd C. Rasmussen,
A. Surjalal Sharma, David E. Siskind, Rigobert Tibi, and Peter E. van Keken, members.
Library of Congress Cataloging-in-Publication Data
Tectonic, climatic, and cryospheric evolution of the Antarctic Peninsula / John B. Anderson and
Julia S. Wellner, editors.
p. cm. — (Special publication ; 63)
Includes bibliographical references and index.
ISBN 978-0-87590-734-5
1. Antarctica. 2. Geology—Antarctica. 3. Geology, Stratigraphic—Cenozoic. 4. Morphotectonics—
Antarctica. 5. Climatic changes—Antarctica. I. Anderson, John B., 1944- II. Wellner, Julia S.
QE350.T42 2011
559.89—dc23
2011040153
ISBN: 978-0-87590-734-5
Book doi: 10.1029/SP063
Copyright 2011 by the American Geophysical Union
2000 Florida Avenue, NW
Washington, DC 20009
Front cover: Schematic diagram of the Nathaniel B. Palmer with the drill rig mounted during SHALDRIL.
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Printed in the United States of America.
CONTENTS
Preface
John B. Anderson and Julia S. Wellner .............................................................................v
Introduction
John B. Anderson and Julia S. Wellner ............................................................................1
A Different Look at Gateways: Drake Passage and Australia/Antarctica
Lawrence A. Lawver, Lisa M. Gahagan, and Ian W. D. Dalziel ........................................5
Exhumational History of the Margins of Drake Passage
From Thermochronology and Sediment Provenance
David L. Barbeau Jr. .......................................................................................................35
Seismic Stratigraphy of the Joinville Plateau: Implications
for Regional Climate Evolution
R. Tyler Smith and John B. Anderson .............................................................................51
Age Assessment of Eocene–Pliocene Drill Cores Recovered During the SHALDRIL II
Expedition, Antarctic Peninsula
Steven M. Bohaty, Denise K. Kulhanek, Sherwood W. Wise Jr., Kelly Jemison,
Sophie Warny, and Charlotte Sjunneskog ......................................................................63
Magnetic Properties of Oligocene-Eocene Cores From SHALDRIL II, Antarctica
Luigi Jovane and Kenneth L. Verosub ...........................................................................115
History of an Evolving Ice Sheet as Recorded in SHALDRIL Cores
From the Northwestern Weddell Sea, Antarctica
Julia S. Wellner, John B. Anderson, Werner Ehrmann, Fred M. Weaver,
Alexandra Kirshner, Daniel Livsey, and Alexander R. Simms ........................................131
Cenozoic Glacial History of the Northern Antarctic Peninsula:
A Micromorphological Investigation of Quartz Sand Grains
Alexandra E. Kirshner and John B. Anderson ................................................................153
Last Remnants of Cenozoic Vegetation and Organic-Walled Phytoplankton
in the Antarctic Peninsula’s Icehouse World
Sophie Warny and Rosemary Askin .............................................................................167
Vegetation and Organic-Walled Phytoplankton at the End of the Antarctic
Greenhouse World: Latest Eocene Cooling Events
Sophie Warny and Rosemary Askin .............................................................................193
AGU Category Index ...................................................................................................211
Index ...........................................................................................................................213
PREFACE
SHALDRIL I and SHALDRIL II presented some formidable logistical challenges. However,
thanks to the hard work of many people, we were able to sample strata from key time intervals
and obtain a record of climate change and associated changes in plants living on and near the
continent. This volume contains detailed results from analyses of the drill core, but it also
contains papers that present the seismic stratigraphic approach to drilling and papers that focus
onthetectonicevolutionoftheAntarcticPeninsula,whichstronglyinfluencedclimatechange.It
represents a synthesis of research by 20 scientists, and we are grateful to all of the authors for
their contributions to this volume. We also thank those individuals who provided constructive
and timely reviews of the papers. Finally, we wish to thank those people who helped with the
logistics, participated on the cruises, and assisted with the research and publication of results.
Therearetoomanytonameall,butwegreatlyappreciatetheirhardworkandpositiveattitudes
duringthebestandtheworstoftimes.Wewouldespeciallyliketothankthosepeoplethatdidso
much to make these first drilling legs happen: Leon Holloway, Jim Holik, Ashley Lowe Ager,
and Andy Frazer.
JohnB.Anderson
RiceUniversity
JuliaS.Wellner
UniversityofHouston
Tectonic,Climatic,andCryosphericEvolutionoftheAntarcticPeninsula
SpecialPublication063
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v
Introduction
John B. Anderson
Department ofEarthScience, Rice University,Houston,Texas,USA
Julia S. Wellner
Departmentof EarthandAtmosphericSciences, University ofHouston,Houston,Texas, USA
Antarctica’s climate and glacial history remain shrouded due largely to a
paucity of outcrops and drill cores; in particular, the Neogene record is
fragmentary. Most outcrops of this age have been studied at some level of
detail, so the greatest opportunity for expanding our knowledge of this time
intervalisthroughacquisitionofdrillcores.Drillcoresfromthedeep-seafloor
around Antarctica have provided a proxy record of climate change and ice
sheet evolution but do notallow us toaddress questions concerning regional
variabilityinicesheetdevelopmentortheresponseoforganismslivingonthe
continenttoclimatechange.Thecontinentalshelfcontainsarichandvirtually
unsampled stratigraphic record, butseaice andicebergslimit accesstothese
areas by conventional drill ships. This has prompted efforts to drill the
continental shelf using unconventional methods, including drilling from the
seaice(ANDRILL)andfromice-breakingresearchvessels(SHALDRIL).
AnunderstandingoftheCenozoichistoryoftheAntarcticcontinentanditsicesheetshasbeen
hinderedbyascarcityofoutcropsthatarenotcoveredbythickice,deepwater,stifftill,orsome
combination of those three. Great advances have been made in recent decades in studies of the
currentAntarcticIceSheetbothontheiceandfromspaceandtheHolocenerecordsaroundthe
Antarctic margin, as well the oceans and biota that surround the continent. Despite the many
advances, the older history of the continent has remained a relative mystery because of the
difficulty in accessing the rocks that hold the record. The few records that are obtained are key
inputstomodelingstudiesoftheAntarcticIceSheethistory[e.g.,PollardandDeConto,2009].
The lack of other long-term records of ice andclimate fluctuations around the Antarctic margin
hindersthedevelopmentandaccuracyofsuchicesheetmodelsandourabilitytolooktowardthe
futurebehavioroftheicesheet.
Tectonic,Climatic,andCryosphericEvolutionoftheAntarcticPeninsula
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2 INTRODUCTION
AroundtheAntarcticcontinentareaseriesofseawarddippingstrata,manyofwhichhavebeen
deeplyerodedduringadvancesoftheAntarcticicesheets.Pre-Pleistocenestrataliejustbeneath
the seafloor, and their distribution can be mapped by high-resolution seismic methods [cf.
Anderson,1999].TheconceptbehindSHALDRIL(shallowdrilling) istodrill throughsurficial
glacialdepositsandsampleolderstratawheretheycomeclosetotheseafloor.SHALDRILwas
never meant for obtaining long cores but, rather, to collect a series of relatively short cores
(~100m)thatcanbepiecedtogether usingseismic records anddetailed chronostratigraphyand
combinedwithseismicstratigraphicinformationtoreconstructclimaticandcryospherichistory.
SHALDRILbeganinearnestin1994withaworkshopsponsoredbytheU.S.NationalScience
Foundation(NSF)andheldatRiceUniversity.Atthattime,theprevailingconclusionwasthatthe
technologywasnotyetreadyforputtingadrillingsystemontoaU.S.AntarcticProgram(USAP)
icebreaker:certainly,thereweresystemsthatcouldhavebeenemployedbutnotwithareasonable
chanceofsuccessundertheharshconditionsexpected.AnydrillingontheAntarcticshelfhadto
contend with pebbly glacial tills, which are notoriously difficult to drill anywhere, freezing
conditions,driftingicebergs,andsubstantialseaicecover,aswellasthefactthatanyicebreaker
brought to the task had not been designed for drilling. A committee was formed to monitor the
technology,andin2001aproposalwassenttotheNSFforademonstrationdrillingcruise.This
proposalbecameSHALDRILIandSHALDRILII.
The research vessel icebreaker Nathaniel B. Palmer (NBP), the primary scientific icebreaker
usedbyUSAPatthetime,waschosenasthevesseltobeusedforthedrillinglegs.Thevesselwas
modifiedby the installation of a moon pool,through which drilling operations could take place
and,later,theintroductionofadditionalballastinordertoaccommodatetheweightofthedrillrig.
These were permanent changes to the vessel, and the moon pool was subsequently used by a
varietyofotherscientificprograms.Seacore(laterFugroSeacore)ofCornwall,UnitedKingdom,
washiredtoperformdrillingoperations.Adrillingrigwascustom-designedtofitontheNBP,and
thisrigwasleasedforthedurationoftwodrillingseasons,cruisesofabout5weeksdurationeach
duringtheaustralfallsof2005and2006.
SHALDRIL I had its first drilling target in Maxwell Bay in the South Shetland Islands and
quickly recovered a long (108 m) core in soft Holocene sediments with high recovery percen-
tages.Unfortunately,thisquicksuccesswouldprovetobeoneoftheonlyscientificsuccessesof
thefirstSHALDRIL season.Thedrilling toolsemployed duringthefirstseasonofSHALDRIL
made very slow progress when drilling through the glacial till, which, in varying thicknesses,
coveredalloftheoldertargetsintheareaeastofJamesRossIslandinthenorthwesternWeddell
Sea.Driftingicebergsmadeitimpossibletostayonstationlongenoughforthetoolstopenetrate
the till, and no pre-Pleistocene material was recovered during SHALDRIL I. Nonetheless, two
additionalHolocenecoreswererecovered:oneeachfromHerbertSoundandLapeyrèreBay.The
threeHolocenecoresobtainedduring2005plustheFirthofTaycorecollectedin2006together
make up the most detailed record of Holocene glacial and climate history around the Antarctic
Peninsula;theyare documented inseveral papers [e.g.,Michalchuk etal.,2009;Milliken etal.,
2009]andarepartsofotherongoingstudies.SHALDRILIhadtechnicalsuccessesalso,reported
in the cruise report (http://www.arf.fsu.edu/projects/shaldril.php) and short articles in Scientific
Drilling and other reports [e.g., Wellner et al., 2005], as well as a great success obtaining
Holocene records. The knowledge base builtduring SHALDRIL I allowedmodifications to the
drillingequipmentandtothegeneralapproachemployedwhiledrillingandthussetthestagefor
the2006drillingleg.
Inthe12monthsbetweenSHALDRILIandSHALDRILII,substantialchangesweremadeto
thedrillbitsanddownholesamplingtoolsusedbytheprogram.Themodificationsimprovedthe
abilityofthedrilltopenetratethroughglacialsedimentandtoobtainsamplesbelowit.Theseaice
ANDERSONAND WELLNER 3
intheWeddellSeaduringearly2006,though,provedtobethickerandmuchmoreextensivethan
normal.Evenworse,theseaiceandtheabundanticebergsweremovingrapidly.Onecore,Site3,
sampledEocenesedimentsoffofJamesRossIslandatthetargetedsite.Thisandothercoreswere
made possible not only by the new equipment and quick actions of the drillers but also by
flexibilitytomovesitesbasedoniceconditions.Furtherreductionsinthetimeneededatanyone
siteweremadebymovingtheshipwiththedrillpipehangingbelow;drillpipewasassembledto
a length just several meters above the seafloor as the vessel continued to maneuver around ice,
thuseliminatingthetimeneededtotripthepipefromthewindowoficeconditionsatanyonesite.
Despite such flexibility, the ice conditions around the primary targets in the James Ross Basin
weresoseverethatplansfortheremainingdrilltargetshadtobeaborted.However,backupsites
along the southern margin of the Joinville Plateau yielded Oligocene, Miocene, Pliocene, and
Pleistocenestrata.Selectionofthesenewtargetswasmadepossiblebycollectingandinterpreting
additional seismic data during the cruise. The cores recovered during this second leg have
provided a record of climatic change and cryospheric evolution that spans the latest Eocene
throughthePleistocene,althoughtherearesignificantgapsbetweeneachcore.
ThisvolumerepresentsthesummaryofthescientificresultsoftheSHALDRILIIprogramas
wellascontributionsfromotherauthorsstudyingthetectonichistoryoftheregion,particularlyas
itrelatestotheestablishmentofoceangatewaysandmountainbuilding.Theseresults,alongwith
thosefromANDRILLandthefewIntegratedOceanDrillingProgramlegsthathavemadeittothe
Antarcticshelf,arebringingthestratigraphichistoryoftheAntarctictolight.Itishopedthatthese
results are just the start, and now that the efficacy of the SHALDRIL approach has been
demonstrated, there will be more drill cores recovered in the near future, including a more
complete record from the James Ross Basin, of which SHALDRIL II has provided just a
tantalizingglimpse.
REFERENCES
Anderson,J.B.(1999),AntarcticMarineGeology,289pp.,CambridgeUniv.Press,Cambridge,U.K.
Michalchuk,B.,J.B.Anderson,J.S.Wellner,P.L.Manley,S.Bohaty,andW.Majewski(2009),Holocene
climateandglacialhistoryofthenortheasternAntarcticPeninsula:Themarinesedimentaryrecordfroma
longSHALDRILcore,Quat.Sci.Rev.,28,3049–3065,doi:10.1016/j.quascirev.2009.08.012.
Milliken,K.T.,J.B.Anderson,J.S.Wellner,S.Bohaty,andP.Manley(2009),High-resolutionHolocene
climaterecordfromMaxwellBay,SouthShetlandIslands,Antarctica,Geol.Soc.Am.Bull.,121(11–12),
1711–1725,doi:10.1130/B26478.1.
Pollard,D.,andR.M.DeConto(2009),ModelingWestAntarcticIceSheetgrowthandcollapsethroughthe
pastfivemillionyears,Nature,458,329–332.
Wellner,J.S.,J.B.Anderson,andS.W.Wise(2005),TheinauguralSHALDRILexpeditiontotheWeddell
Sea,Antarctica,Sci.Drill.,1,40–43.
J.B.Anderson,DepartmentofEarthScience,RiceUniversity,Houston,TX77005,USA.(johna@rice.
edu)
J. S. Wellner, Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX
77204,USA.
A Different Look at Gateways:
Drake Passage and Australia/Antarctica
Lawrence A. Lawver, Lisa M. Gahagan, and Ian W. D. Dalziel
Institute for Geophysics, UniversityofTexasatAustin,Austin,Texas, USA
ThetimeoftheopeningofDrakePassagebetweenSouthAmericaandthe
Antarctic Peninsula is problematic. Mammals were able to migrate between
South America and Antarctica until sometime in the early Eocene. Various
continental fragments may have formed an effective barrier to substantial
deepwater circulation through Drake Passage until at least 28 Ma. Alterna-
tively, a medium-depth to deep water passage may have existed through
Powell Basin to the south of the present Drake Passage as early as 33 Ma,
but it is difficult to constrain the time of opening of Powell Basin. Simple
opening of a shallow seaway between southern South America and the
Antarctic Peninsula does not produce a vigorous Antarctic Circumpolar
Current(ACC).Othergatewaysmustbeopentomedium-depthtodeepwater
circulation such as one between the South Tasman Rise and East Antarctica.
Even mid-ocean plateaus may play a role in the ultimate development of a
circum-Antarcticcurrent.Themostprobablesouthernoceanfeaturethatmay
have affected global circulation was the opening of a deep seaway between
the Kerguelen Plateau and Broken Ridge at about the Eocene-Oligocene
boundary. While a complete deepwater (>2000 m) circuit was certainly
developed by the end of the early Oligocene, it may have been the closure
ofamajordeepseawaynorthofAustraliainthemiddleMiocenethatfinally
produced the environment for the development of a vigorous ACC.
1. INTRODUCTION
The opening of southern ocean gateways has long been considered a significant factor in not
onlytheinitiationoftheAntarcticCircumpolarCurrent(ACC)butalsointhedevelopmentofthe
CenozoicEastAntarcticIceSheet[Kennett,1977].TheEocene-Oligoceneboundarystepinthe
∂O18 anomaly history [Zachos et al., 2001, 2008] at 33.7 Ma (timescale from Berggren et al.
[1995]) is taken as a proxy to represent the onset of Antarctic bottom water formation at
temperatures close tofreezing [KennettandShackleton,1976]and,inturn,thefinalopeningof
Tectonic,Climatic,andCryosphericEvolutionoftheAntarcticPeninsula
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6 A DIFFERENT LOOKAT GATEWAYS
Figure1.PolarstereographiclocationmapshowingtheAntarcticCircumpolarCurrent(ACC)derivedfrom
the work of Sandwell and Zhang [1989] as black arrows. Deep Sea Drilling Project and Ocean Drilling
Projectsitesareshownasnumbers.Thepresent-dayplateboundaryisshownasathingrayline,whilelarge
igneousprovincesareshowninadarkgray.Magneticanomalypicksareshownascrosses,whilemagnetic
isochrons are shown as lines parallel or subparallel to the plate boundaries. Lines orthogonal to the plate
boundariesarefracturezonelineationspickedfrombathymetryderivedfromsatellitealtimetrydata[Smith
and Sandwell, 1997]. Abbreviations are BR, Broken Ridge; DP, Drake Passage region; KP, Kerguelen
Plateau;PB,PrdyzBay;LG,LambertGraben;STR,SouthTasmanRise;TAS,Tasmania.
acircum-AntarcticseawaythatisolatedAntarctica.Lyleetal.[2007]supportalateOligoceneto
earlyMioceneinitiationofanACCbasedonsedimentationintheSouthPacificbackedbygrain
size evidence from the Tasman Gateway [Pfuhl and McCave, 2005]. Based on neodymium
isotope ratios at Agulhas Ridge, Scher and Martin [2004] support an initial opening of Drake
Passage as early as middle Eocene, although Livermore et al. [2005] suggest only a possible
shallow seaway development at Drake Passage perhaps as early as middle Eocene with a deep
seaway only developing between 34 to 30 Ma coincident with the increase in the high latitude
∂O18 values at the Eocene-Oligocene boundary. The ACC shown in Figure 1 is presently the
largest ocean current with an eastward flow rate through the Drake Passage region of 136.7 ±
7.8Svbasedonthebaroclinictransportrelativetothedeepestcommonlevel[Cunninghametal.,
2003]. In the region of the Scotia Sea shown in Figure 2, they found that the ACC transport is
principallycarriedintwojets,theSubantarcticFront(SAF),whichaccountsfor53±10Sv,and
the Polar Front (PF), which accounts for 57.5 ± 5.7 Sv. Southward of the main ACC, they
calculatedthattheSouthernAntarcticCircumpolarCurrentFront(SACCF)transports9.3±2.4Sv.
LAWVERETAL. 7
Figure 2. The ACC fronts for the Scotia Sea region, digitized from Figure 1 of the work of Naveira-
Garabato etal.[2002], superimposedon thebathymetry ofthe regiontakenfrom themost recentonline
version(August, 2010)oftheworkofSandwellandSmith[1997].Frontsarelabeledinwhite:PF,Polar
Front; SACCF, Southern ACC Front; SAF, Subantarctic Front; SB, Southern Boundary of the ACC.
Geographical features are labeled in black: BB, Burdwood Bank; Br, Bruce Bank; DB, Discovery Bank;
FI,FalklandIslands;MEB,MauriceEwingBank;PB,PirieBank;SAM,SouthAmerica;SG,SouthGeorgia
Island;SO,SouthOrkneyblock;SRP,ShagRocksPassage;SSA,SouthSandwichArc.
ThelocationsofthefrontsthatdefinetheACCintheScotiaSearegion(Figure2)aretakenfrom
theworkofNaveira-Garabatoetal.[2002],whohavetheSAFcurlingaroundtheeasternendof
BurdwoodBankbeforeheadingnorthacrosstheeasternendoftheFalklandPlateauandshowthe
PFexitingthecentralScotiaSeaatagapinthenorthScotiaRidgewestofAuroraBankatabout
48°W(labeledtheShagRocksPassage).Consequently,themajorityoftransportoftheACCexits
acrossthenorthScotiaRidgetothewestof48°W,wellwestofSouthGeorgiaIsland.TheSACCF
curls around the eastern tip of South Georgia to flow westward through the Northeast Georgia
PassageofNaveira-Garabatoetal.[2002].TheremainderoftheACCcurrentflowisboundedto
the south and east by the Southern Boundary of the ACC and does not flow directly eastward
acrosstheSouthSandwichArc(SSA)asmightbeexpected;rather,itexitstheScotiaSeaatthe
deepest point along the northern margin of the east Scotia Sea at about 30°E. It is clear that
substantialACCtransportisdependentonmedium-depthtodeepwaterpassageways,seemingly
thoseatleast2700mdeep.AnanalogtotheACCmaybetheinteroceanexchangeofthermocline
water[Gordon,1986],whichrunsintoachokepointintheLombokStraitoftheSundaArcwhere
only 1.7 Sv out of the 7 to 18.6 Sv Indonesian Throughflow [Gordon and Fine, 1996;
Gordon et al., 2003] passes through the strait which has a sill depth of ~300 m. The remainder
ofthethroughflowisdivertedover1000kmtotheeasttoentertheIndianOceanviatheTimor
Troughwhereasilldepthof1300to1500misfound.Consequently,theimpactoftheopeningof
Drake Passage to deep water flow is critical to understanding its impact on Cenozoic climate.
WhileashallowDrakePassagemayhaveopenedduringtheEocene,itsimpactontheCenozoic
climatemayhaveonlybecomesignificantwhenadeepwaterpassagefinallyopened.
As shown in the ∂O18 compilation of Zachos et al. [2008], the world’s oceans began to cool
after the early Eocene Climatic Optimum (EECO) (equal to ~53 to 51 Ma), well before the
Eocene-Oligoceneboundary.ItisimportanttodeterminebothwhenaCenozoiclandbarrierfirst
disappearedintheDrakePassageregionandwhenadeepseawayfinallydeveloped.Withrespect
tothedevelopmentofaseawayorconversely,theeliminationofa“landbridge”betweenSouth
AmericaandtheAntarcticPeninsula,thebestindicationmaybewhenmammalswerenolonger