Txu-Oclc-32363355.Pdf (14.41Mb)
Total Page:16
File Type:pdf, Size:1020Kb
Zilker Park Walking Tour Guidebook: ARecreationalVisit totheEdwardsLimestone A SPORTINGEVENT OF THE GULF COAST ASSOCIATIONOF GEOLOGICAL SOCIETIES 1994 CONVENTION, AUSTIN,TEXAS,OCTOBER5-7,1994 PREPAREDBY JenniferL.Walker AND PaulR.Knox ZilkerPark Walking Tour Guidebook: ARecreationalVisit to theEdwardsLimestone A SPORTINGEVENT OF THE GULF COAST ASSOCIATIONOF GEOLOGICAL SOCIETIES 1994 CONVENTION, AUSTIN,TEXAS,OCTOBER 5-7,1994 PREPAREDBY Jennifer L.Walker AND PaulR.Knox Contents Zilker Park Walking Tour Guidebook: A Recreational Visit to the EdwardsLimestone JenniferL.Walker and Paul R.Knox INTRODUCTIONIntroduction Overview 1 UsingtheGuidebook 1 How to Make theMost of Your Visit Gettingthere 2 Your options 2 Beprepared 5 GEOLOGIC SETTINGOFTHE ZILKERPARK AREA StratigraphyandDepositionalSetting Overview 7 General stratigraphy 7 Paleogeographic setting 7 Sequence framework 12 Detailedstratigraphy 12 Structural Setting 14 ZILKERPARK TRAIL GUIDE(5-KMLOOP) Introduction 17 Stop 1:Cretaceous Tidal-flatDeposits 17 Stop 2:Stone-FacedPillars 21 Stop 3:Barton SpringsPool 21 Stop 4:Zilker Ponds 24 Stop 5:BartonCreek TerraceDeposits 26 Stop 6:TheMoonlight Tower 26 Stop 7:Zilker Park DinosaurTrackways 26 Stop 8:The AustinNature Center 27 Stop 9:TheButlerLandfill 27 Stop 10:The "Rock Island" Outcrop 30 Returnto theParkingLot; ClosingtheLoop 32 Optional Stop:Umlauf Sculpture Gardens 32 TheHome Stretch:BartonCreek below BartonSpringsPool 33 BARTONCREEKGREENBELT GUIDE (10-KMLOOP) Introduction 35 Getting Started Some cautionary notes 35 Where tobegin 35 Stop 4: Solution-Collapse Zone 36 Stop 5:Campbell'sHole 36 Stop 6: SmallFault above Campbell'sHole 36 Stop 7:New Wall 39 Stop 8:Gus Fruh Wall 39 Stop 9:Barton CreekGravelBars 40 Stop 10: BartonCreekFault Revisited 40 Stop 11: Airman's Cave 42 ACKNOWLEDGMENTS 46 REFERENCES 47 Introduction Overview ZilkerPark and theBartonCreek Greenbelt are true gems inthe crown of Texas' capitalcity. Theserecreationsites are unique inthat they are large oasesofopenand undeveloped areas within 2 miles ofa statecapitol. This is especially true of the greenbelt, where you feel that youare miles from civilizationunlessyoucatchthe occasional viewof ahouse behind the bigoak trees at the top of the canyon walls.The pristinenatureofBarton Creek andBartonSprings is zealously guarded bymany Austinites, whohave attempted torestrict building anddevelopment within theBarton Creek drainage area topreventwater-qualitydamage. Within this area areoutcrops ofa regionally important stratigraphic unit, theEdwardsLimestone.TheEdwardsis akey element within theEdwards aquifer, whichsuppliesall of the water usedby themore thanonemillionresidentsof themetropolitan SanAntonio area andwhich feedsthe sparklingpool atBartonSprings. TheEdwardsLimestoneis also amajorreservoir ofoil andgas,having produced more than319 million barrels ofoil(Galloway andothers, 1983),andmore than2 trillion cubic feet ofgas (Kostersandothers,1989). Additionally, itis animportant source ofbuilding stone and cement. Thisguidebook directsparticipants on an informal walkingtour through the ZilkerPark area andtheBartonCreek Greenbelt.The touris dividedinto two parts:Part onedescribespoints ofgeologic interestalong aloop approximately 5km(3.1miles) long,whichcirclesthrough ZilkerPark, BartonSprings, ZilkerBotanicalGardens, Dinosaur Trackways (only openSaturday,October 8, from 9 a.m. to 3p.m.), the Austin Nature Center,theTownLakeHike andBike Trail,andother optional attractions.Part two guidesparticipants pastBarton Springs andalonga 10-km (6.2-mile) loop ofa segmentof theBartonCreek Greenbelt toview extensiveEdwards exposures andfluvial featuresofBartonCreek. Thegreenbelt is anarrow strip ofundeveloped acreage inthe canyon of BartonCreek andis rimmed by urban growth.The canyon contains an extensiverangeof geological andbiological features thatcharacterize thediverse Central TexasHillCountry. The trailsurfaceis even (sandy and gravelly)in mostplaces but rocky in some, is designed to be passable formountain bikes,andhas verylittle elevation gain. These tours are designed tobe self-guiding. As aresult, youare free tochoose when you take the tour andwhichroute you willfollow. However,theoptimal time for the 5-km tour willbe on Saturdaymorning,October 8, following theconvention.Thisis because themost interesting stop on the5-kmroute,theDinosaur Trackways,is only openon Saturdays, andwe have made special arrangements to extenditsnormal hours(9 a.m. to 11a.m.),making it available from9 a.m. to 3p.m. Whichever tour you choose, we hope this willbean opportunity for some exercise andrelaxationbefore beginning the journeyhome. UsingtheGuidebook Theremainderof theguidebook is brokeninto four sections; (1)How to Make the Most of YourVisit, which gives youdirections on how toget tothepark, tells you enoughabout the5-km and10-kmroutes tohelp youdecide whichisright for you,and spells out some cautionary notes;(2)Geologic Setting of theZilker Park Area, which sets the stage for what you will see during your tour, (3) ZilkerPark TrailGuide(5-Km Loop), whichincludes theDinosaurTrackways(open Saturday from 9 a.m. to 3p.m.); and(4) BartonCreek Greenbelt Guide(10-KmLoop). Read the first two sectionsbefore you visit thepark tohelp youplan yourvisit Becauseboth loops share thefirst several stops, you shouldstart at theteginning of the5-kmloop guide,regardlessof whether you eventually take thelonger or theshorter tour. HhowtoMakethe Mostof Your Visit Getting There Gettingto Zilker Park is relatively easy (Figure 1). Barton SpringsRoadis a major thoroughfarethatruns east-west on thesouth side of TownLake.Itruns right through theheartof thepark. From downtown,go southon Congressor Guadalupe across TownLakeandturn right (westbound)onBartonSpringsRoad.Ifyou'revisiting without acar, consult the CapitalMetrobus scheduleandmapenclosedinthispacket From thedowntown hotels, take theappropriate route to Congress andthentransfer toaRoute 30bus going south.It will turnright (west)ontoBarton Springsroadheading towardthepark. Ifyou'recoming fromout of townor from the far northorsouthof town,you'll most likelybe traveling onInterstateHighway35 orLoop 1(MoPac to the locals,named after theMissouri-Pacific railway, who donatedpart ofitsright-of way to makeroom for amajor stretchof thefreeway).FromInterstateHighway35,exit atRiversideDrive going west,then turn left onBartonSpringsRoad justafter passing- Congress Avenue. FromLoop 1, going south,exit at Route 2244(Rollingwood WestlakeHills),take the U-turnleft underthe freeway overpass,andproceed northon the frontage road, which borders the west side of thepark. This willbend to theright(eastward)andbecome Barton SpringsRoad.Ifyouhave been travelingnorth onLoop 1,theRoute 2244 exit willput youdirectly ontothe frontage roadgoing north. The tours start attheRock Gardenparking area (Figure 2).Ifyou arecoming from the east along BartonSprings road, take thefirst left turn onto thenarrower side roadafter youenter thepark, thenbranchright immediately,going slightly uphill, to enter theparkingarea, andpark in thesection totheleft.If entering thepark fromthe west,from Loop 1(MoPac),take the firstright turn after the Zilker GardenCenter sign, and follow itdirectly to theparkingarea. YourOptions This walkingtour ofZilker ParkandBartonCreek Greenbeltreplaces the5-km and 10-kmruns commonly scheduled forgeological conventions.Thepurpose of this eventis to providetheopportunity for some outdooractivity that at thesame timegives insight into aregionally important stratigraphic unit,all withinAustin'sunique and treasured ZilkerPark andBartonCreek Greenbelt.This guidebook contains trailguides for a5-km (3-mile) loop throughZilkerPark anda10-km (6-mile) loop along theBarton Creek Greenbelt,within the steep-sided andundeveloped BartonCreek Canyon.Youcan run,walk,or bike your selected route,depending on yourpreferredform ofexercise. If youpreferbiking,but didn't bring your trusty steed, see below for bikerental information.In addition,canoes are availableforrentalalong the5kmroute ifyou want to getout onto TownLake(see the5-km loop section "TheHome Stretch:BartonCreek below BartonSprings Pool"). Which loop youselect depends on your level ofenergy and thetype of features you wish to see.Tlie5-kmloop is idealfor aslowerpace, withmany stopsandsights.It gives youadetailedview of outcrops and acquaints you with some of Austin'scultural features, at the sametime offering youadditionaloptionssuch ascanoe rides anda visit to a sculpture garden. Oneof themore popular stopsis theDinosaur Trackways, which record theroamings of several species across a tidalmudflat approximately 99 million years ago.Unfortunately, this featurecan beopenonly oneday during theconvention (Saturday,October8, from9 a.m. to3p.m.).Tickets arepurchased as youenter the fenced-insite. Ifyou wish toassure a visit to this stop,pleaseplan accordingly. Among other things youmay wishto bedivertedby,thereareplentiful picnic areas throughout thepark,plus Softball andbaseballfields, an officialFrisbee golf course, volleyball 2 (MoPac) 1 GCAGS Loop the and from35 excerptedHighway ismap thisInterstateofrespectively. of portion thoroughfares exits, A Drive area.main Park the Zilkerfrom and accessRollingwood/Westlake Easy the Austin and Drive downtownreference.for mapof Riverside StreetBrochure by 1. provided FigureConvention are 3 the 5-km in the and outcrops lotlarger parking and Garden trail, Rock greenbelt the the at of pointbeginning starting the the to tour, the route of drivingroute the and stops showingthe Park are ZilkerNoted