Geology of the Flinders Ranges National Park

Oraparinna

Brachina Gorge

Slippery Dip

Aroona Ruins/Cultural Heritage Site

Bunyeroo Valley

Sacred Canyon Cultural Heritage Site

Arkaroo RockCultural Heritage Site

St Mary Peak St Mary Peak St Mary Peak St Mary Peak St Mary Peak St Mary PeakMalloga Falls

To Black Gapvia Heysen Trail

BridleGap

To Hawker40 km

Bunyeroo Bunyeroo Bunyeroo Bunyeroo Gorge Gorge Gorge Gorge Gorge

Bunyeroo Gorge

HucksLookout

Stokes HillLookout

To Leigh Creek100 km

Appealinna RuinCultural Heritage Site

Dingley Dell

Youngoona

Trezona

Yanyanna Hut

To Arkaroola160 km

WilkawillinaGorge

Koolamon

To Parachilna Gorgevia Heysen Trail

To Blinman13 km

Cambrian

AcramanCampground

Red HillLookout

BrachinaEast

Teamsters

Aroona Valley Aroona Valley Aroona Valley Aroona Valley Aroona Valley

BunyerooValleyLookouts

WILPENA

POUND

PerawurtinaCulturalHeritage Site

Rawnsley Bluff

Wilpena

Elatina Hut

Mt OhlssenBagge

TanderraSaddle

Dedman's Hut

Great Wall of China

To Hawker viaMawson Trail

CooindaCampWangarra

Lookout

HillsHomestead

Brachina

Self

Guided Drive

Water (may be insprings/creeks)

Phone

Fuel

Accommodation

Caravan camping

Vehicle based camping

Bush camping

Ranger station

Self-registration station

Lookout

Bus parking

Heysen Hut

Park boundary

Sealed road

Unsealed road

Walking trail

Walking trail(mentioned in this brochure)

Heysen Trail

Mawson Trail

Ruin

Building

Information

Toilets

Parking

Hawker

CarrietonQuorn Port

Augusta

Wilmington

Copley

Marree

WirrealpaBlinman

Parachilna

LeighCreek

Lyndhurst

To Innamincka

Gammon RangesNational Park

Lake

Torrens

National

Park

Strzelecki Track

Lake FromeRegionalReserve

Flinders RangesNational Park

MER 203996

Walk safely

Be prepared when bushwalking:

•Wearsturdyshoes,hatandsunscreen.

•Carrysufficientfoodanddrinkingwater—allow4litresofwaterperpersonperday.Donotrelyontanksorcreeksintheparkfordrinkingwater.

•Keeptothedefinedwalking.trail.

•Informaresponsiblepersonofyourproposedrouteandexpectedtimeofreturn.

•Weatherconditionscanchangequickly;ensureyouhaveappropriatewetweatherclothing.

TrailTime *DistanceTrail NotesClassification

Wilkawillina Gorge Hike6hoursone-way

11.4kmone-way

Habitatofyellow-footedrockwallaby;uniquegeologicalfeatures.

Hard

Bridle Gap Hike6hoursreturn

18.8return

TheWilpenaPoundisfilledmainlywithrecentalluvium;observewildlifethroughthePound.

Hard

Bunyeroo and Wilcolo Creeks Hike

5hoursreturn

9.2kmreturn

Nativepinegrovesalonghilltops;cool,gum-linedcreeks.

Moderate

YulunaHike4hoursloop

8kmloopThishikeleadsthroughthelandscapethatinspiredartistHansHeysenonhisnumerousvisitstotheFlindersRanges.

Moderate

Haywards Huts Hike Network

TrezonaHike4hoursloop

8.2kmloop

DiscoverfossilsofsomeoftheearliestlifeformsonEarthintheTrezonaFormation.

Hard

AroonatoYoungoonaHike

7hoursone-way

15kmone-way

Alinearwalkacrossthepurpleshaleofthenativepine-cladABCRangetothelimestoneoftheTrezonaRange.

Hard

St Mary PeakHike

directroute(outsidetrail)

6hoursreturn

14.6kmreturnBreathtakingviewsof

thecentralFlindersRanges.

Hardlooproute(insidetrail)

9hoursreturn

21.5kmreturn

Heysen Trail1500km

TheHeysenTrailisgenerallyopenfromApriltoOctobereachyear.ItisclosedduringtheFireDangerSeason.Datesvaryfromsectiontosection,andfromseasontoseason.

*Time is generously estimated from an average walking speed of 2 km per hour –allow extra time for resting and sightseeing.

HIKE – Moderate•somemoderateinclines•irregularsurfacewithloose,unevenbase

•averageleveloffitness

HIKE – Hard•somesteepinclines•irregularsurfacewithloose,unevenbase

•averageleveloffitness•somehikingexperience

Heysen Trail cont.Thesouthernsection,fromCapeJervistoSpaldingintheMidNorth,followstheMountLoftyRangesandisidealforbeginnersandthosewithchildren.Thenorthernsection,fromSpaldingtoParachilnaGorge,isisolatedandattimesrugged,providingarewardingchallengeforexperiencedwalkers.

Thetrailhasbeendesignedtocaterforboththeseriousbackpackerwalkingthecompletelength,andforthedaywalkerwhomightchoosetodoshortwalksalongdifferentsections.Forfutherinformationsee<www.environment.sa.gov.au/parks/pdfs/FLRA_PDFS_PARK_GUIDE.PDF>and<www.heysentrail.asn.au/heysen_trail/>.

ThestoryoftheFlindersRangesbeganmorethan800millionyearsagoduringtheNeoproterozoicEra,whentheEarthwasundergoingmajorchangesinitscrustandsurfaceenvironments.Thelandwasdevoidofplantsandanimals,andtheoceanswerepopulatedonlybymicroscopicorganisms.Itwasalsoatimeofbreak-upofverylargecontinentallandmasses,similartothemuchlater(about100millionyearsago)break-upthatformedthepresentcontinents.

TheFlindersRangespresentamagnificentrecordofEarthhistory.Withcarefulobservations,therocksdisplayedintheruggedrangesandcolourful,gum-linedgorgescanbereadlikeabook,takingusonalongjourneythroughtime.Thishistoryisrepresentedinasuccessionofrocklayers,nowtiltedanderoded,andhenceaccessibleattheEarth’ssurface.Thelayersconsistofdifferenttypesofmainlysedimentaryrocks,eachdepositedunderdifferentconditionsofenvironmentandsedimentsupply.Theserocklayers,termedformations,areeachuptohundredsofmetresthick.Theyrecordrepeatedadvancesandretreatsoftheseaandchangesinclimate,includingtwomajoriceages.

TheoldestrocksseenintheFlindersRangesNationalPark,theCallannaGroup,providecluestotheearliestoriginsoftheranges.Foundonlyintwolargestructuresknownasthe

OraparinnaandEnoramaDiapirs,theserocksarebrokenanddisruptedsedimentarybedsoriginallydepositedinshallow,restrictedseas,coastallagoonsandsalinelakes.Castsofsaltcrystalsarecommonlyfoundontheunder-surfacesofbeds.Lavaflowsandashfallsrecordedinthesesedimentswerederivedfromvolcanicactivityasmoltenrockrosealongdeepfracturesinthecrust.

Atthistime,about800millionyearsago,theEarth’scrustwaspulledapartandthinned,forminganextensivesedimentarybasinastheseastartedtofilltheresultingdepression.Thisbasin,knownastheAdelaideGeosyncline,stretchedfromnearOodnadattatoKangarooIsland.

About700millionyearsago,severeclimaticcoolingledtoamajoriceage,whenglaciersandicesheetscoveredmuchofAustraliaandothercontinents.Theglaciersscoureddeepvalleysinthelandscape,pickinguprockdebristhatbecameincorporatedintheiceandwaslaterreleasedastheglaciersmelted.Suchglaciallyderivedsedimentistypicallyamixtureofmud,sand,pebblesandboulders;whencompactedandhardenedthisformsarockcalledtiIIite.Inthepark,thePualcoTilliteandthedarkred,ridge-formingHolowilenaIronstoneweredepositedduringthisglaciation.SiltstoneoftheoverlyingWilyerpaFormationrecordsgradualwarming,withoccasionalcobblesandpebblesdroppedfrommeltingicebergs.Prominentridge-formingsandstoneatthetopoftheWilyerpaFormation,forexampleneartheLovesMineRange,wasdepositedoff-shorebystormcurrentsfromsandfreedbymeltingicealonganancientshoreline.

Arapiddeepeningoftheseafollowed,duringwhichblack,organic-richmudsoftheTapleyHillFormationweredepositedthroughouttheAdelaideGeosyncline.

TheOraparinnaandEnoramaDiapirsfirstbecameactiveatthistime.TheoriginofthesestructuresisthoughttobeduetotheoriginalpresenceofsaltbedsintheCallannaGroup.Saltislighterandmoreductilethanotherrocktypes.Astheoverlyingpileofdensersedimentsthickenedwithcontinuingdeposition,thesalt-bearingmaterialbecameunstable.Faultingalongzonesofweaknessin

theunderlyingcrustmayhavebeenthetriggerthatinitiatedupwardmovementofthelessdensesedimentsoftheCallannaGroupundertheweightofthickoverburden.Thismovementdraggedupanddisruptedthebeds,formingabrecciaoffragmentsofsedimentaryrocks,aswellasblocksofvolcanicrock,fromtheCallannaGroup.

Atfirst,theoverlyingbedsweredomedupwardsasthesalt-bearingmaterialrose.Later,thediapirperiodicallybrokethroughtothesurface,anddiapiricbrecciaspilledoutontheseafloororonsmallupliftedislands.Thismaterialwasreworkedbycurrentsintothemarinesedimentsofthetime,forminglenticularconglomeratelayersasseen,forexample,intheTapleyHillFormationaroundthemarginsofthediapirs.Thefine-grained,grey-greensandstonebedsofMountCaernarvonrecordgradualshallowingofthebasinasitbegantofillwithsediment.

TheSunderlandFormationofthecentralFlindersRangesalsoconsistsoffine-grainedsandstoneandsiltstone,butitsbaseisanerosionalboundary,resultingfromadropinsealevelandmarkedbyathin,coarse-grainedsandstone.ChannelswerecutintotheunderlyingTapleyHillFormationandfilledwithooliticandpebblylimestone.Sealevelthenroseagain,

depositingfinergrainedsedimentsbut,asthebasinfilledup,shallowmarine,sandytogrittylimestoneoftheEtinaFormationaccumulated.Large,trough-shapedscoursindicatehigh-energywaveandcurrent-influencedenvironments.TheOraparinnaDiapirwasagainactiveatthistime,sheddingfragmentsofCallannaGrouprockstoformconglomeratelensesintheEtinaFormationadjacenttothediapir.Interbeddedgreen,siltyshalesrecordquieter,deepermarineepisodes,asdoestheoverlyingEnoramaShale.

TheTrezonaFormationmarksareturntonear-shore,tidallyinfluencedandlagoonalenvironments,idealforthegrowthofcyanobacteriawhichbuiltupstromatolites(seeStromatolites).

Atthistime,sealevelfellwiththeonsetofanotherglacialperiod.LimestoneoftheunderlyingTrezonaFormationwassubjecttodissolutionbyrainwater,producingakarsttopography.GlaciationisrecordedbythepebblysandstoneandlocaltiIIiteoftheElatinaFormation,containingglaciallyderivedpebbles,manystriatedorgroovedbyrocksgrindingagainsteachotherwhilecarriedbyice.

Aprominentyellow-weatheringpinkdolomite,theNuccaleenaFormation,wasthendepositedastheseaagainfloodedthebasinwithareturntowarmerclimates.Thethicksiltstoneandfine-grainedsandstoneoftheoverlyingBrachinaFormationinturnrecordsoverallshallowingofthebasin,culminatinginthedepositionofbeachsandmakinguptheABCRangeQuartzite.Cross-beddingandripplemarkswereformedbytidalcurrents,andmudcracksindicatethatthinclaylayerswereoccasionallyexposedanddriedout.

Afterabrieferosionalinterval,therewasanothermajormarinefloodingofthebasin.ThemonotonousredshaleoftheBunyerooFormationwasdepositedindeep,quietwater.Withinthisformation,auniquelayerofrockdebris,onlya

fewcentimetresthick,isthoughttorepresentthefall-outfromtheimpactofalargemeteoritethatstruckthepresentpositionofLakeAcramanonnorthernEyrePeninsulaatthistime.

Beforesedimentationwasabletofillthebasinagain,itwaspunctuatedinthesouthernandnorthernFlindersRangesbythescouringofcanyonsuptoakilometredeep,causedbyrenewedstretchingofthecrust.Theparkarea,however,wasmorestableandthisremarkableeventisrecordedbyaperiodofveryslowdepositionofaone-metrethick,bandedyellowdolomitemarkingthebaseoftheWonokaFormation.Thebasin,includingthecanyons,wasquicklyfloodedbythesea.Deep-watergreenshaleoftheWonokaFormationpassesupwardsintolimestoneandsandstonedepositedasthebasinagainbegantoshallow.Grazingtrailsofsmallworms,thefirstgoodevidenceofmarineanimallife,arefoundinthisformation.

TheWonokaFormationpassesupintotheredBonneySandstone.Ripplemarks,mudcracks,mudpebblesandcross-beddingrecordshallowdeltaicandtidalenvironments.

ThewhiteRawnsleyQuartziteformsthehighestbluffsandrangesoftheparkarea.Ittoowasdepositedinshallowmarineandpossiblyfluvialenvironments.Closetothebaseisaunitofsiltstoneandthinlybeddedsandstonewhichcontainsthefirstabundantevidenceofcomplexmarineanimallife(seeEdiacaraFauna).

AttheendoftheNeoproterozoicEraabout540millionyearsago,theseawithdrewcompletely.Afteraperiodofterrestrialerosion,thebasinwasagainfloodedatthebeginningoftheCambrianPeriod,whenthefirstanimalswithhardshellsevolved.IntheparkareathefirstCambrianrockunitistheParachilnaFormation,consistingofwhite,clayeysandstoneandsiltstonewithlong,verticalandU-shapedwormburrows.

Geological history of the Flinders Ranges

203996-002

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PortAugusta

Broken Hill

Arkaroola

Marree

WilpenaChalet

PortLincoln

ADELAIDE

SA

QLD

NSW

Initial stages in development of the Adelaide Geosyncline. Tectonic forces stretched and thinned the Earth’s crust, forming an extensive low-lying basin that was invaded by the sea. Volcanoes and lava flows formed along zones of crustal weakness.

Development of the Oraparinna Diapir. Initially, less dense Callanna Group rocks intruded zones of weakness in overlying sediments. As the diapir continued to rise, it breached the seafloor and detritus was shed into flanking sediments.

Sea

Diapir

Detritus Seafloor

INITIAL STAGE

LATER STAGE

Tapley Hill Formation

Wilyerpa Formation,Holowilena Ironstone,Pualco Tillite

Burra Group

Callanna Group

203996-001

Contact between the white Rawnsley Quartzite (weathering orange) and underlying red Bonney Sandstone, Brachina Gorge. (Courtesy of Bernd Stoecker; photo 044285)

Ripple marks in the Rawnsley Quartzite, Wilpena Pound, looking towards Chace Range. (Courtesy of Bernd Stoecker; photo 044287)

800 million years ago

Thefirstreefssimilar,forexample,totheGreatBarrierReefgrewinshallowwarmwatersduringtheCambrian,butthesewerebuiltnotbycorals,butbysponge-relatedanimals,nowextinct,calledarchaeocyaths.ThesearebeautifullypreservedinpartsoftheWilkawillinaLimestone.InWilkawillinaGorge,theParachilnaFormationismissing,andthelimestoneliesdirectlyovertheBonneySandstone.

Later,adropinsealevelcausedexposuretthereefs,formingakarstterrainwithmanysinkholesfilledwithiron-richsilt.

Thedarkgrey,organic-richlimestoneoftheMernmernaFormationwasdepositedasthebasinagainflooded,forminganextensiveseaforthelasttime.TheoverlyinggreenOraparinnaShaleincludesthefirsttrilobites,preservedinconcretions.Asthebasinagainbegantofillwithsediment,coarsesiltandsandweredeposited.Thebasinhadbecomeveryrestricted,allowingthedepositionofshallow-waterredsandandsiltoftheBillyCreekFormation

andLakeFromeGroup.However,thisdepositionwasinterruptedbyabriefmarineintervalrepresentedbytheWirrealpaLimestone.

SedimentationfinallyceasedwhenmajormovementsandheatingwithintheEarth’scrustbeganabout500millionyearsago.Bynowtheaccumulatedsedimentshadbeencompactedandcemented.Convergentmovementoftheancientstablelandmassesoneithersideofthebasincausedbucklingandupthrustingofthesedimentaryrocks.Theparkoccupiesabroad,deeplyerodedanticline,withtheoldestrocksinthecentreandstratatiltedinoppositedirectionseastandwestofthiscentralcore(cross-sectionAA’).WilpenaPoundformsagentlesynclineandtheMountBurnsareainthesouthwesterncornerofthemapformsatighteranticline(cross-sectionBB’).Duringbuckling,largefaultsandfracturesformedalongzonesofweaknessandre-activatedfaultsthathadbeenactiveduringsedimentation.

Duringfolding,thediapirsbecamethecoresoflargedome-shapedfolds.Thesalt-bearingdiapiricmaterialwasfurthercompressedandmobilised,andinjectedhigherintotheoverlyingrocks.Latererosionhascutthroughthedomes,providingaviewofthedeeperlevelsofthediapirs.

Asaresultofthismountain-buildingactivity,theancestralFlindersRangeswereborn.Weatheringanderosionimmediatelybegantoreducethemountainsastheyrose.Largeriverscarriedawayvast

amountsoferodedrocktotallingseveralkilometresinthickness,tofeedthedevelopingsedimentarybasinsineasternAustralia.Byabout100millionyearsago,theancestralrangeshadprobablybeenreducedtoalow,gentlyundulatinglandscape.Earthmovementsrelatedtothebreak-upofAustraliafromAntarcticathencausedreneweduplift.Duringthelast50millionyears,theFlindersRangeshavebeenrisingsteadily,andpersistentsmallearthtremorsindicatethatthisisacontinuingprocesstoday.

FluvialandlacustrinesedimentationoccurredinvalleyssuchasattheentrancetoBrachinaGorge.Softmudstoneunitswereerodedreadilytoformvalleys,whilehardrockssuchasquartziteremainedaspeaksandridges.ThespectacularBrachinaandBunyerooGorgeswerecutthroughbyriverswhichexploitedjointsandsmallfaultsinthesandstoneridges.Thesedynamicprocessescontinuetoshapetherangesbut,withadrierclimatetoday,sedimentaryprocessesarelimitedtooccasionalfloodeventswhenlargequantitiesofsand,gravelandboulders,aswellasup-rootedtrees,maybecarrieddown-stream.

Asyoucanseethereismoretotherangesthanfirstmeetstheeye.TheevidenceofthislongperiodofEarthhistoryisavailabletothekeenobserverofthecluespreservedintherocks.Thisunderstandingcanonlyenhancetheuniquebeautyoftheranges,oneofourmosttreasuredholidaydestinations.

Otherdiscsmayrepresentsoft,possiblytentacle-bearingpolypswhichwereattachedtotheseafloor.Alsopreservedasimpressionsontheundersidesofbedsareprimitiveworms,animalswithacoelome(bodycavity)ofarthropodaffinities,ancestorsofseaurchins,andsomecompletelyenigmaticforms.

Cambrian trace fossils TheU-shapedburrowsintheParachilnaFormationindicatethattheburrowingwormshadarigid,fluid-filledbodycavity.ThefactthattheysoughtshelterinburrowsindicatesthatpredatorsmusthaveevolvedbytheEarlyCambrian.

Cambrian shelly fossils TheCambrianlimestonescontainthefirstfossilsofanimalswithhardskeletons.Theseincludethecup-shapedarchaeocyaths,whichwereprobablyfilterfeedersrelatedtosponges,andwhichdiedoutlaterintheCambrianPeriod.Molluscs,includingsmallseasnailsandcockle-likeshells,brachiopods(Iamp-shells),andtheextincttrilobites,canalsobefoundintheCambrianlimestonesandshales.TheseanimalgroupsallappearedearlyintheCambrian,representingthemostdramaticexplosionofdiversityinthehistoryofevolution.

Fossils

Fourgroupsoffossilsarepresentinthepark:stromatolites,theEdiacaraFauna,tracefossilsandshellyfossils.Eachrepresentsadistinctstageintheevolutionoflife.

Stromatolites Theoldersedimentaryrockscontainnoevidenceofanimallife.Onlyprimitive,largelysingle-celled,microscopicorganismslivedinthesea.Someofthese,beingphotosynthetic,wereresponsibleforgraduallybuildinguptheoxygencontentoftheatmospheretoapointwhereanimallifewasabletoevolveatsometimelateintheNeoproterozoicEra.

Nofossilsoftheancientmicro-organismsarepreservedintactinthepark,however,thereisabundantevidenceoftheiractivityinsomelimestoneunits,e.g.TrezonaFormation.Cyanobacteria(formerlyknownasblue-greenalgae)flourishedontheshallowseafloor.Matsformedbytheirintertwinedmicroscopicfilamentstrappedfinesedimentaryparticlessuspendedinthewaterandcausedchangesinwaterchemistry,duetophotosynthesis,whichallowedcalciumcarbonatetoprecipitate.Thisformedthinlimylayersand,asthematsgrew,theybuiltupthelaminatedstructuresknownasstromatolites.Dependingonthetypesofmicro-organismsinthematsandontheshapingeffectsofthelocalenvironment,stromatolitesmaytaketheformofwavylaminations,domes,cabbage-shapedstructures,

broadcolumns,orslender,branchingcolumnsandfingers.Examplesofthewavylaminated,dome-shapedandbroadlycolumnartypescanbeseenintheTrezonaFormation.

The Ediacara Fauna AnimalfossilsfirstappearintheWonokaFormation,butbecomeabundantintheRawnsleyQuartzite.

Theseanimalsweresoftbodiedandarepreservedasimpressionsonquartzitebeds.KnowncollectivelyastheEdiacaraFauna,theyofferourfirstusefulglimpseofearlyanimalevolution.Theyaredominatedbycircularimpressionsuntilrecentlythoughttobeoffree-floatingjellyfish.However,mostofthecircularformsaremorelikelytobeburiedanchoringdevices(orbulbs)offrond-likeanimals.

Stromatolites in the Trezona Formation. (Photo 042161)

Wilkawillina Gorge. Reddish Bonney Sandstone overlain by lighter Rawnsley Quartzite and darker Wilkawillina Limestone on the ridge. (photo 042160)

CAINOZOIC Quaternary

Tertiary Neogene

MESOZOIC

Palaeogene

Cretaceous

Jurassic

Triassic

PALAEOZOIC

Permian

Carboniferous Pennsylvanian Silesian

Mississippian Dinantian

Devonian

Silurian

Ordovician

Cambrian

NEOPROTEROZOIC NeoproterozoicIII

Cryogenian

Tonian

MESOPROTEROZOIC

Stenian

Ectasian

Calymmian

PALAEOPROTEROZOIC Statherian

Orosirian

Rhyacian

Siderian

ARCHAEAN

1.6

23

65

141

205

251

298

354

410

434

490

545

1000

1600

2500

GeologicaltimescalerepresentedintheFlindersRanges

Era Period Millionsofyearsago

Worm burrows in the Parachilna Formation. (photo 042163)

Mawsonites, an Ediacara fossil (x 0.4).(photo 038763)

Archaeocyaths in the Wilkawillina Limestone, Brachina Gorge (x 0.6). (photo 038766)

Dickinsoniacostata in the Ediacara Member, Rawnsley Quartzite, Brachina Gorge (x 0.7). (Photo 042162)

Trilobite from the Oraparinna Shale. (Courtesy of Jim Gehling; photo 408458)

Wilkawillina Gorge(11.4 km one-way)

TherocksalongthiswalkaresimilartothoseexposedalongBrachinaGorgebutthesequencedipsintheoppositedirection(east)asitisontheothersideofabroaddomalfold(anticline).AtWilkawillinaGorge,agraben(fault-boundeddepression)developedwithintheAdelaideGeosynclineasitwasfillingwithsediment.Foldingofthesedimentsinthegeosynclineabout500millionyearsagocausedthegrabentobetippedontoitsendsothat,fromabove,itssedimentscanbeseeninsection.

ThewalkbeginsinBrachinaFormationsiltstoneandABCRangeQuartzitebeforecrossingthesedimentaryrocksboundedbyfaultsofthegraben.ThesequencewithinthegrabenincludeslimestoneandsiltstoneoftheWonokaFormation,BonneySandstoneandWilkawillinaLimestone.AhighlightofthegorgesectionistheoutcropsofWilkawillinaLimestonecontainingexcellentexamplesoffossilsofthecoral-likearchaeocyatha.

Unlikethewesternpartoftheranges,theeasternrangescontainlittleRawnsleyQuartzite.AftertheRawnsleysandsweredeposited,mostofthetoplayersintheeastwereremovedbyerosionbeforetheCambrianlimestoneswerelaiddown.TheWilkawillinaLimestoneinthisareathereforeoverliestheBonneySandstoneandnot

theRawnsleyQuartziteasinthewesternranges.

Bunyeroo and Wilcolo Creeks (9.2 km return)ThisloopwalkthroughrollinghillsoftheBunyerooValleycommencesonBrachinaFormationsiltstoneandsandstonewhichdisplayripple-markedsurfacesindicativeoftheshallow-wateroriginofthisformation.ThewalktraversestheABCRange(ABCRangeQuartzite)andreddishBunyerooFormationshale.

Haywards Huts Yuluna (8 km loop), Trezona (8.2 km loop) and Aroona to Youngoona (15 km one-way)

Therearethreewalkstochoosefrom:twoloopsofabout8kmateitherendofaone-waywalkof15.4km.AttheAroonaValleyend,thewalkpassesthroughtheABCRange(ABCRangeQuartzite)whichshowslayersofsediment,ripplemarks,jointsandfolds.Attheotherend,thewalkpassesthroughtheTrezonaRange(TrezonaFormationlimestoneandshale)wheredome-shapedstromatolitesexposedinEnoramaCreekprovideevidenceofearlylifeonEarth.TilliteoftheElatinaFormation,depositedduringaperiodofglaciation,isexposedinEtinaCreek.ThebroadbandofcountrybetweentheABCandTrezonaRangesisoccupiedbysoft

BrachinaFormationsiltstonewhichgivesrisetoalandscapeoflow,rollinghills.

St Mary PeakDirect route (14.6 km return) Loop route (21.5 km return)

Thispeak,composedofRawnsleyQuartzite,providesviewsofthebasinofWilpenaPoundtothesouthand,tothenorth,rowsofrangesstretchingtothehorizon.

Bridle Gap(18.8 km return)

ThiswalkacrossWilpenaPoundwhichcanbestartedeitheratWilpenaChaletorBlackGapinMoralanaValley(outsideoftheNationalPark).ThetrailfromtheChaletviaPoundGaptraversestheredBonneySandstoneandoverlyingwhiteRawnsleyQuartzite.Aftertheruinoftheoldhomestead,thecentralpartofthePoundisfilledmainlywithrecentalluvium.

Heysen Trail(1500 km)TheHeysenTrailpassesthroughsomeofSouthAustralia’smostdiverseandbreathtakinglandscapes,traversingcoastalareas,nativebushland,ruggedgorges,pineforestsandvineyards,aswellasrichfarmlandandhistorictowns.Itincludesnationalparks,stateforestsandinternationallyacclaimedtouristdestinations–theBarossaValleyandthestunningWilpenaPound.

Hawker to Blinman RoadArkaroo Rock ArkarooRockisalargefallenboulderofsandstoneshedduringtheerosionofWilpenaPound.AcavecontainingAboriginalrockartwasformedbyfrettingofsandstonethroughtheactionofmoisture.

Rawnsley Bluff Lookout (Just south of the park boundary)

ThislookoutprovidesanexcellentviewofthesouthernendofWilpenaPound.WhiteRawnsleyQuartziteformsthehighpeaksoftherimofthesynclinalstructure.Belowthecliffs,theslopesareformedofredBonneySandstonewhichoverlieslightcolouredWonokaFormation.

Onenteringthepark,theroadfollowsredshaleoftheBunyerooFormationfor10km.About0.5kmaftertheWilpenaChaletturnoff,theroadpassesthroughagapintheABCRange(ABCRangeQuartzitewhichdipstothewest).Forthenext10km,theroadpassesthroughprogressivelyoldersedimentaryrocksincludingthinpinkdolomiteoftheNuccaleenaFormation,reddishsandstoneoftheElatinaFormationandgreylimestoneoftheTrezonaFormation.

Hucks Lookout Thislookout,locatedongreysiltstoneoftheTapleyHillFormation,

providesexcellentviewsofWilpenaPoundandthecompletewest-dippinggeologicalsuccessionfromTapleyHillFormationtoRawnsleyQuartzite.

Stokes Hill Lookout Thislookout,alsoonTapleyHillFormation,providesviewstowardsWilpenaPoundtothesouthwestandOraparinnaDiapirtothenorth.

Forthenext12km,theroadpassessubduedoutcropofmainlyshallow-dippingTapleyHillFormation.AfterOraparinnaStation,theroaddescendsthroughstratawhichdipgentlynorthwestandbecomeprogressivelyyoungerforthenext7km.TheseincludeflaggydolomiteoftheWockerawirraDolomiteMemberandcraggyoutcropsoflimestoneoftheEtinaFormation.AftertheBrachinaGorgeturnoff,

greenEnoramaShaleistraversedforabout10kmuntilthenorthernboundaryoftheparkisreached;alongthewesternsideoftheroadisthedistinctiveTrezonaRangecomprisedofalternatingbedsoflimestoneandsiltstoneoftheTrezonaFormation.

TheroadinthisareaisalsoattheclosestpointtotheEnoramaDiapirwhichispoorlyexposedonalowridge500mtotheeast,about1kmnorthoftheparkboundary.HeredolomiteoftheEtinaFormationoverliesmucholderbasaltraftedupbythediapir.

Great Wall of China Locatedsome7kmnorthofthepark,thisfeatureistheerodedcliff-edgeofaresistanthorizontalbedoflimestonewithintheEtinaFormation.

Brachina Gorge(18 km one-way) Thisdrive,whichstartsattheturnoffontheHawker-BlinmanRoad,containsfamouslandmarksinEarthhistory.TheroutecutsthroughrocksoftheAdelaideGeosynclinewhichrangeinagefrom650millionto520millionyears,andexhibitsoneofthemostcompletesedimentaryrecordsintheworldforthisage.Theserocksprovideauniquerecordofthegeologicaleventsandclimaticconditionsprevalentatthetimetheyweredeposited.Theyarethewesternremnantofalargedomalfoldandbecomeprogressivelyyoungertothewest,includingthesequencefromEnoramaShaletoWirrealpaLimestone.

SheltersateitherendofthedriveprovidegeneralinformationonthegeologyofBrachinaGorge.Stopsalongthewayinterpretfeaturesofinterestincluding:•stromatolitesintheTrezonaFormation,representingsomeoftheearliestlifeonEarth

•evidenceofaniceageintheElatinaFormation

•evidenceintheBunyerooFormationofameteoriteimpact600millionyearsago

•fossilsoftheEdiacaraFauna,amongsttheoldestknownsoft-bodiedanimals,intheRawnsleyQuartzite

•thefirstanimalswithskeletonsandshellsintheWilkawillinaandWirrealpaLimestones.

A more detailed brochure on the Brachina Gorge Geological Trail is available from PIRSA.

Wilkawillina Gorge Road AfterleavingtheturnoffontheHawker-BlinmanRoad,theroadcrossessubduedrollinghillscomposedofTapleyHillFormationsiltstone.About5kmaftertheturnoffisafaultedcontactbetweentheTapleyHillFormationandbrokenanddistortedrocksoftheOraparinnaDiapir.Outcropofdiapiricbrecciacontainingraftsofsedimentaryrocksandboulderybasaltoccursalongtheroadsideforthenextfewkilometres.MountCaernarvonintheLovesMineRangecanbeseenontheeasternhorizon.About2kmpasttheturnofftoWilkawillinaGorge,theroadturnseastwardalongabroadvalleyofBunyerooFormationshale.TothenortharethespectaculartreelesshillsoftheWonokaFormation,whiletheABCRangeQuartziteformsthesouthernwallsofthevalley.

Bunyeroo Valley(27 km one-way) OnleavingtheBunyerooValleyturnoff,theroadpassesthroughopencountryonshaleandlimestoneoftheTrezonaFormationforadistanceof13km.AfterYanyannaHut,theroadtraversesyoungerrocksuntilreachingBunyerooValleyLookout.

Bunyeroo Valley Lookout ThislookoutislocatedonsiltstoneoftheBrachinaFormationandprovidessweepingsoutherlyviewsalongthevalleyofBunyerooCreektowardsWilpenaPound.Aselsewhere,therimofthepoundiscomposedofwhiteRawnsleyQuartziteunderlainbyredBonneySandstone.TheroadthenfollowsBunyerooCreekthroughtheABCRangeandturnsnorth,traversingpurplishshaleoftheBunyerooFormation.

Drives Hikes

Rawnsley Bluff at the southern end of Wilpena Pound. Cliff-forming Rawnsley Quartzite overlies Bonney Sandstone. (Photo 042164)

Northern rim of Wilpena Pound from Bunyeroo Valley lookout, showing light coloured Rawnsley Quartzite overlying red Bonney Sandstone. (Photo 042165)

(Cover image courtesy of SA Tourism Commission; photo 043528)

©GovernmentofSouthAustralia

Firstpublished1994

Reprintedwithadditions2011

cont.

Location of hikes in the Flinders R anges National Park