STROMATOPOROID PALAEOECOLQGY AND SYSTEMATICS FROM THE MIDDLE DEVONIAN FANNING RIVER CROUP. NORTH QUEENSLAND Al EX G.COOK Cook, A.G. I4V9 ()6 30: Siomalopoioid palueoecologv and systematic 1mm the Middle Devonian Fanning River Group, north Queensland. Memoirs oi the Queensland A//; 43(2). 463-551 Brisbane. ISSN 0079-SS35. . Thirty five slTomatoporoidlaxa are described from the Middle Devonian (Givetian) lower Fanning RiverGroup, Burdekin Subproviuce, north Queensland. \ustmlia. Ten faunal communities are recognised, based on the study and distribution of stromatoporoid and selected molluscnn ta\a, and the distribution oftabulate and rugose corals. The Burdikiniacommunity, characterised by robust gastropods, occupied thecoarse siliciclastic innershelf. The ModiOmutpkacommunity isrepresentedbyanear-shore, insitu shell bed. The Stacbyodes catituJata-Syringppora community lived in inner shell'muddy carbonate-dominated lagoons, but was in partable to inhabit subtidal interstitial niches of marine headlands. In the Fleteherview-Burdekin Downs area, theHermatostromamaetifafl Germnostromahendersonicommunity constructed lagoonalpatchreefs,back-reeflaminar strontfltoporoidpavementsand biohemis. i'he C/athr»coilanaspi&sthAuloporacommunity occupied nearshore, fringing biostromes in the Fanning River area. Ferestromatijpora heideekeri-A/nph/pora ramosa-Strmgocephalus community occupied extensive nearshore to offshore biostromes within the Panning Rivet-Golden Valley areas. The Cogfto&troritfi- Hermatvstroma episcopate Community dwelt within dispersed stromatoporoid pavements and less commonly, within offshore coralline thickets. The Amphipora pervesicutata community characterised b\ dendroid stromaloporoid-coralline thickets adjacent to and seawardofbioherms, dispersed stromatoporoid pavements and stromatoporoidbiostromes, particularly in the Fleteherview-Burdekin Downs area. The Endopfyllnxn community was restricted to patch reefs which grew during a regressive phase, carbonate to siliciclastic transition.Acephalopodassociationisrepresentedbyasparsefaunaoccurringwithindeeper water micritic fades in theGolden Valley area. Analysis ofstromatoporoid shape demonstrates the influence ofboth genetic and ecologie factors. Zonalionofskeletal shape, apparent lor both biostromal and biohermal complexes, indicatesthat strong ecologie influencesdominated.Substrate l\pe. sedimentationrate and waterdepth were important controls. Most taxa display a range ofshape. Complex over- growth phenomena, between stromatoporoid taxa, tabulate corals, chactetids and algae produced compound skeletonsthat are most common v\ithin nearshore biosirome-s, and are interpretedto indicatestress imposed by repeated lethal depositionat events or by season.il variations in salinity. Inlergrowihs ofstromatoporoids with tabulate corals Syr'wgOporellef} sp. and SyrjrtgOp0r& s-p.,anumberofrugosecoralsanda ,'vermelidaredocumented. nireliiflsp. Ismore common instromatoporoids with irregularskeletal architecture. ForSyrrtigoporellcflsp.an evendistribution ofcorallites withinThe host, skeletal response to corallite occurrence and the absenceofrnicritk envelopes suggests a symbiotic relationship with boththe coral and die stromatoporoid accreting at the same rate and maintaining an even growth surface. Six new species ofstromatoporoids are described comprising Gerronostroma hcmlcrsom, Trupvfosiromozha- }ffiphipo?Qmerfini, Feresiromatonoraheideckeri Cocftostroma bwdekinen.se and Coenosiroma wyuiri. Biogeographic affinities ofthe fauna are strongly with the Old World Realm, with S] s I level affinities with Guangxi, Poland and Belgium. CI Stromatoporoids. taxonomy, north Queensland, Middle Devonian, palcreoecokjgy Ue,\ G. Conk. QueenslandMuseum. POBoyJ3Q\ , >'. Australia; , [February ?999 Stromatoporoids are major faunal elements of Subprovince, Townsville hinterland, north the ?Eifelian-Givetian Farming River Group, Queensland. This study examines the ecology which cropsout extensively within the Burdekin and systematica ofthe stromatoporoid faunas 464 MEMOIRS OF THE QUEENSLAND MUSEUM plain coarse-grained fluvial channel and finer-grained floodplain deposits. Deposition within the inner shelf was complex reflecting local influences of coarse siliciclastic input, inner shelf carbonate production and an across-shelf siliciclastic to carbonate transition. Facies deposited in the inner shelf are: (1) abraded coarse siliciclastic faciesrepresenting inundated marine headlands, and coarse siliciclastics representing upper shoreface deposition, (2) fossiliferous sandstone facies deposited on thelowershorefacetosubtidal zone, (3) fossiliferous siltstone facies, representing restricted fine-grained siliciclastic- Legend LateDevonian-EarlyCarboniferous dominaled, nearshore, subtidal (KCe)elbottomGroupand CollopyFmn embayments, (4) nodular Camazoicsediments,oasallsand Lata Devonian DalswoodGroup limestone facies deposited laterites MiddleDevonianFanning RiverGroup within mostly subtidal, ELaartleyCPaerbnomnainfeirno|urus-,itvoo:, aanssdemEabrllaygeDsevoniancarbonate-clastic carbonate-dominated, impure CLIoanntsteoilnCveaenrntbcaoylnGiCulflaeslrtyoiuG(5sCetSnoytbriEalalr)GlyroPueprmjiMaWn). eCElaaarmslteyilcDseCv(rKoe)neikanSumbaprrionveinccatr1bOotndaotviecsiiainndiu ldaegvoeolnospwmietnhtl,oca(l5)paticmhpurereef LateCartiBntierousvotcantcsand Ravenswood Balholilh limestone-sandstone facies vHoellclasniGcaltaesliHchsyo(lEti=e)EllenvaleBertsH= representing sporadic depos- EarlyCarbonilerousGranites PMreetcaamionrbprihaincsArgentine: ition of mobile coarse PrecainbrianRunning siliciclastic sand bodies vEaorllcyanCiacrsbu(Imnlcolruoduitng.Galriednr[oochkr-.Gsur..oup) aPinvdotKiMrketRaimvoerrpBheidcss((FN)W) within impure, subtidal carbonatelagoons.Deposition FIG. 1.GeologicalmapoftheBurdekinSubprovineeafterLangelal.(1990). on the proximal shelf was dominated by stromatoporoid The Fanning River Group is the lowermost biostromal facies (seven divisions) representing stratigraphic unit ofthe Burdekin Subprovince, a biohermal (reefal) deposition (framestone), Middle Devonian to Carboniferous succession back-reef or intra-biostromal stromatoporoid WSW ofTownsville(Fig. 1). TheGroupconsists pavement(eoverstone), interreefchannel (grainy of 3 formations; Big Bend Arkose, Burdekin floatstone), and extensive biostromes and Formation andCultivation Gully Formation. In a storm-reworked equivalents which developed recent sedimentological study (Cook, 1995), 12 from the nearshorezone acrossthe shallow shelf distinct facies have been identified from the (silty aibbly floatstone, micritic stromatoporoid Middle Devonian, ?Eifelian~Givetian Big Bend floatstone, rudstone, associated packslone and Arkose and Burdekin Formation, ofthe Fanning wackestone). Reef and biostromal growth took R. Group. They represent deposition within the place during moderate levels of siliciclastic restricted Burdekin Basin in non-marine, inner input,incloseproximitytothegranitichinterland and proximal shallow water marine shelf, and and can be considered as preserved "fringing1 shallow to moderate depth, distal marine shelf reef and biostrome. Additionally where environments. Non-marinc deposition extensive reefor biostrome did not develop, the (unfossiliferous coarse siliciclastic facies) took proximal shelf was inhabited by dispersed place within restricted coastal plains, and stromatoporoid pavements (dispersed represents in situweatheringprofiles and coastal stromatoporoid packstone facies). Three facies STROMATOPOROIDS FROM THE FANNING RIVER GROUP 465 represent distal shelf deposition, seaward of Etheridge & Foord (1884) described 2 coral taxa biohermal or biostromal growth: (1) coralline andonechaetetidtaxonfromtheReid'sGaparea. packstone, representing shallowwater, offshore, Jack & Etheridge (1892) described and coral and dendroid stromatoporoid thickets, (2) illustrated many faunal elements from the localised crinoid grainstonc deposited as mobile Burdekin Formationaspartofthemonograph on carbonate sand bodies on the shallowdistal she!I the Geology and Palaeontology ofQueensland. removed from significant siliciclastic input, (3) Included were the first description and micriticcarbonatefades,restrictedtotheGolden illustrations ofstromatoporoids from the region Valleyarea, representingrelatively deeperwater with Stromatopora described and illustrated and deposition at the limits of the photic zone. Stromatoporella illustrated but not described. Endophyllum siltstone facies represents growth Etheridge 191 7a) erected the gastropod species of small, coral-dominant patch reefs in a Pofyamma( burdekinensis subsequently revised fine-grained mixed carbonate-siliciclaslic by'Knight (1937) and Heidecker (1959). environmentduringinitial stagesofregression in Etheridge (1917b) described the polyzoan the uppermost Burdekin Formation within the Vetoflstula miribaiis from the limestones at Fanning R. area. ReicTs Gap, but this has subsequently been Deposition was controlled by basement referred to as a species of the tabulate coral topography and restricted basin geography with Cladopora(Hill 1981), sairgneivfiiecwanotfvatrhieatsitornastiagcrraopshsytsheeesuDbrparpoevrin&ce.LaFnogr coHriallls(1f9r42o)mm3adeloacadleittaiielsedisntudtyheofBthuerrduegkoisne (1994), or Cook (1995). Subprovince; Fanning R., Burdekin Downs and Stromatoporoids are dominantly found within Raid's Gap. She illustrated and described 23 the Burdekin Formation, which based on the species of rugosans and mentioned the ramose eonodontstudiesofTalent& Mawson 994)has stromatoporoid Amphipora, the brachiopods (1 been assigned a mostly Givelian age; see also Atrypa and Stringocephalus, and the gastropod Cook (1995). Pofyamma. Shealsoassignedamid-Givetianage tothebedsbasedon theirsimilaritiestoEuropean Localities mentioned in this reportaredetailed faunas. Brown (1944) briefly described in Cook (1995). Material is deposited at James Stringocephalus burtini Defrance from Fanning Cook University of North Queensland, with a R.and Reid'sGap,alsoattributingaGivetianage sCPmroeaoflkilxeUcsnoiluvlseeercdtsiiiotnnytgahteisoltwohogeirckQaulaerelenocsJalClaiUtnyLdafMnoudrsJJeaCumUme.Fs tdoesctrhiebeldi4memsotlolnuescaunnitgse.neHraei(d1ebcikvearlve(1a9n5d9)3 gastropods) ofwhich 3 were new, from the Big forJames Cook University Fossil collection. Bend Arkose and Burdekin Formation near Lowes Basin. In Hill, Woods & Playford (1967) PREVIOUS PALAEONTOLOGICAL an unnamed stromatoporoid and a number of STUDIES molluscan, rugose coral and tabulate coral taxa from the Burdekin Formation were illustrated. Palaeontological investigations ofthe Fanning Strusz( 1969) and Strusz & Jell ( 1971 ) discussed RiverGroupcommencedwith theworkofClarke rugose coral taxa from the Fanning R. Group. ( in Leichhardt 1 847 ) who described West (1974) recognised 3 informal ^Cyathophyllum leichkardtT from the Burdekin biostratigraphic zones as part of a study ofthe (R1iv8e8r0.),NicEhthoelrsiodng&e E&theFroiodrgde ((11887894)),.EtJhaecrkidg&e rspu.gonsoewcorraanlsgeatzoFnaen,nitnhge RS.tr:itnhgeopTheymlnloupmhsypl.lucfm. Etheridge (1892) and Etheridge (1917a, 1917b) quasinormale assemblage, and the Endophyllum all contain descriptions and lists of fossil abditum columna range zone. West (1974) & collections from the Burdekin. Nicholson inferred an early- to mid-Givetian age for the Etheridge (1879) also described a number of sequence but qualified the utility ofthese zones tabulate corals from the Fanning R. and Arthurs withadiscussion ofthe facies dependence ofthe Ck areas. They also briefly documented the coralline forms. In addition, West (1974) presence ofStromatopora and Caunopora from mentioned and illustrated a number oftabulate ' Arthurs Ck. representing the first record of corals and Amphipora spp. Stephenson (1977) stromatoporoids from the Burdekin. Etheridge documented a number of rugose and tabulate (1880) described 5 brachiopod taxa from the corals from the Fletcherview area. Henderson Fanning R. area collected bv RobertLoaanJack. (1984) discussed the diagenetic origin ofsilica 466 MEMOIRS OF THE QUEENSLAND MUSEUM withina *Hermatoporoidea, type stromatoporoid Early Devonian allochthonous stromatoporoids from Fanning R. A major study of the rugose oftheJesseLimestone,NewSouthWales. There coral faunawas undertakenbyZhen (1991) who are a number publications which list Australian identified 10 coral assemblages within the Devonian stromatoporoids, including Benson Fanning R. Group sensit lato, comprised of79 (1922), Teichert & Talent (1958), and Philip species and subspecies distributed amongst 41 (1960,1962). This summary does not include the generaofrugosecoral.Zhen(199] )providedthe largenumberofminorreferencesthatareoflittle basis forrugosecoral identifications giveninthe taxonomic value. Several ofthese are listed in present work. He briefly noted the presence of Flugel & Flugel-Kahler (1968). Most recently some stromatoporoid taxa, but did not attempt Webby & Zhen (1997) have published part of their systematic evaluation. Jell et al. (1988) theirongoingworkonthestromatoporoidfaunas recorded the crinoid taxon Cupressocinites from the adjacent Broken R. Province. abbreviates Goldfixss from Big Bend and an indeterminate crinoid from Herveys Range PALAEOECOLOGY outcrops of the Burdekin Formation. In more recenttimesCook(1993a,b; 1997)hasexamined Cook (1995) established 11 marine fades molluscs frompartsoftheFanningR.Group,and within the Big Bend Arkose and Burdekin Zhen (1994) and Zhen & Jell (1996) have Formation providing an ecostratigraphic formalisedsomeoftherugosecoraltaxa.Zhen& framework for faunal study. Zhen & Jell (1996) West (1997) described some symbionts in both established a broad, basin-wide model for the stromatoporoids and chaetetids from the Fanning R. Group, representing the coral and Burdekin Formation. sedimentologic associations. Here a more detailed ecological roles, inter-relations and AUSTRALIAN DEVONIAN responses to different environments of the STROMATOPOROID STUDIES. stromatoporoids and other selected organisms preserved in the Big Bend Arkose and Burdekin Systematic and palaeoecologic work on Formation will be discussed under 5 headings: Australian Devonian stromatoporoids is sparse. 1) Stromatoporoid shape, and shapegroupings Stromatoporoids have been mentioned present in stromatoporoid-bearing fades. commonly, listed infrequently and described rarely. To date the works of Ripper (1933, 2) Differences in shape groupings between relatedfadestoestablishwhetherzonationexists 1937a,b,c,d, 1938),Mallett(1968, 1970a,b, 1971), and Cockbain (1984, 1985), Webby, Steam & across reefoid facies, and to investigate which Zhen (1993) andWebby& Zhen (1997) formthe factors most strongly influence stromatoporoid shape. main body ofDevonian stromatoporoid work. 3) Diversity in shape within individual In Victoria, description of Early Devonian stromatoporoid taxa. stromatoporoids from Lilydale (Ripper 1933, 1937b), Loyola(Ripper 937c),Buchan(Ripper, 4) Relationships between stromatoporoids and 1 1937d) culminated in a synthesis of their other organisms, assessed from intergrowth and assemblages by Ripper (1938). She also overgrowth phenomena to determine if described Ampkipara ramosa (Phillips) from inferences of the physical environment can be Western Australia. The Lilydale, Buchan, Tyers made from such characteristics. and Waratah Bay stromatoporoids were 5) Community groupings of stromatoporoid reviewedby Webby, Stearn & Zhen (1993). and other faunal elements, their partitioning and Mallett (1968, 1970a,b, 1971) described overlap, their guild structure, and the role of stromatoporoid faunas from the Broken R. individual taxa within the guild structure. Province. Cockbain (1984) described 25 species In addition the palaeobiogeographic affinities ofstromatoporoids from the Canning Basin reef andrelationshipsofthefaunaarealsodiscussed. complexes. Western Australia. Thetaxa range in age from Givetian to Famennian. A small fauna STROMATOPOROID SHAPE of stromatoporoids from the Carnarvon Basin was described by Cockbain (1985). Shorter Stromatoporoid shape was controlled by both worksincludethoseofEtheridge(1911), Dun(in ecologic and genetic factors (Kapp, 1975; Benson 1918), Cockbain (1979) and Cockbain Kershaw & Ridina. 1980; Kershaw, 1981, 1984, (1989). Webby & Zhen (1993) described the 1990; Stearn, 1982a; Kano, 1990). Analysis of STROMATOPOROIDS FROM THE FANNING RIVERGROUP 467 developed by many authors 30- N - including Broadhurst (1966). 4U,. Abbott (1973), Kershaw & Riding (1978), Cockbain (1984), and Kano (1990). In n i- this, and the following chapter ilu dealing with the systematic descriptions of the fauna, the terminology of Kershaw & Riding (1978) is used, withthe addition of2 terms introduced by Cockbain I9S4): < "stachv odiform' and 'amphiporiibnrf. Thus the terminology used herein ts: laminar (with a height to base ratio < 1:10), low domical, medium domical,highdomical (extended domical ofKershaw Na|1,779 & Riding (1978)), bulbous, irregular, dendroid comprising staehyodiform and amphi- IMG.2. Stromaloporoid skeletal morphology from patch reefenvironment;, poriform. oftheBurdekinFormation.Bivariateplotsshow verticalheight(V)versus Some authors [e.g. Kobluk, basal width (B) in centimetres. Triangularplots show vertical height (V) 1975; Kano, 19903) have basal width (B) and diagonal distance (D) following the method of Kershaw & Riding(1978), with diagonal angle set at 2j\ A, (.781 patch attempted to graphically reel approximately 23m above base of section. B, L77-8 patch reels display the size groupings of afpapdreosxaipmpartoexliym1a3tneillyabokvmebNasoefokfs7e7c8t.ion,C.Patchreefinspotexposureof sstirmopmlaetopploortotodfswbiydthuseveorsfusa I height. Althoughtheprocedure skeletal growth shapemayprovideuseful insights gives a good indication ofsize it was notedthat it into the palaeoecology of fossil reefal and does not adequately quantify the shape of the biostromal organisms, hut there is littleconsensus organisms, leading Kershaw & Riding (1978) to on the precise influences of environmental parametense stromatoporoid shape using conditions on shape. Many authors have made percentileratiosofvertical height(V), basalwidth pajaeoecologica] inferences based onthe study ui' (B) and diagonal distance (D) at a set angle (q) both eross colonial shape in relation to substrate plotted on a triangular diagram or triplot. For (Kapp 1975, Kershaw & Riding 1978, Kershaw comparative purposes, their method provides a 1981, 1984, 1990, Bjerstedt &>eldmarui 1985, simple, quick, graphical display ofshapedomains Kfllto 1990), and relationships ofcolony margins within fades or communities. Kershaw t\: l1o97e5n;clKoesirnsghaswed&imeRnidtisng(,Bro1a9d7h8t;irKset.rs1h9a6w6,; 1K9a8p4p),, Riinddiincga'tsin(g19t78h)e asphparpoeaschofis lqaurigtee,usreefguullairn Several authors have argued for lateral and stromatoporoid skeletons and those of other vertical zonation within stromatoporoid-bearing groups. However the method has the following s1t9raXt5a)(aKonbdlusko,me197h5a;veBjeartstteedmtpt&edFteoldrmealnant.e disadvantages' ( 1 ) There is no dimensional scale stromaloporoidshape groupings, to combinations fnoer\tehrersekperleesteonnt.e(d2a)sThseomenetifroerfmiseldaroenutnhaetttraiipnlaobtlies of ecological conditions such as oxygenation in siromatoporoids. (3) The method does not turbulence,andsedimentationrate(StJean, 1971 Bjerstedt & Feldmann, 1985; Kano, adequately representdendroid formsand doesnot I! deal with irregularforms. (4)Themethod requires Kershaw. 1990). either full specimen collection, generally Fora qualitative assessment ofstromatoporoid impossible with the Burdekin fauna, corrects, shape it is important to maintain consistent 'oblique' data , 01 excellent, vertically exposed terminology. Gross skeletal terminology hasbeen sections through the keletons. d 46« MEMOIRS OF THE QUEENSLAND MUSE1 'M Nevertheless |he method ofrepresenting shape laui.s is a useful benchmark with which to coventonafadiu compare stromaioporoi occurrences and combined with the more traditional base versus height plots, and i. i provides a useful graphical [i I. ! I characterisation for the assemblages. Data were collected from representative stromatoporoid-domiriant FIG. 3. Stromatoporoid skeletal rftorphologj BoiiP coverstone facies oi the Facies to characterise ibc Rurdekin Formation. Bivariatepintsshow vertical height Y versus basal | ) giteonne-rdaelnsdhraopiedssdtormoamiantospoofrotihde v. iidditlhi ii BB)) airnidcednitaigmoentarles.disrtrainacnegu(fDe)u pflootl:l-,owsihnogwthveermtiectahlohdeiogfhtKe(rV)s,habwasa&l fauna, field measurements Riding (I9?B), with diagonal angle set at 25". A. LSOj. LippermpsJ facies were made with a simple Sed within RopeladderCave. H. L7SL faciesimmediately imuciK irjg measuring tape, reading Lo the hiohcrmat unit. nearest 0.5cm. sedimentation rate (Broadhurst. 1966; Tsien in STROMATOPOROIDSHAPE WTI HIN PA TCI Steara L982a; Bjerstedt & eldmanm 1985), 1 I REEFS, Two t\ pes ofpatch reefs were identified which could not have exceeded rates within the within the nodular limestone facies by Cook nearer shore lagoons supporting patch reefs. ( 1995); columnar, bulbous til pillar shaped reefs Indeed in the eoverstonc facies o( L.S03. the and diffuse patches ofeovcrsione-framstone. laminar dominant forms occur at the top of an Both types show a dominance of large, low energy waning cycle suggesting a relative domical forms (Fig. 2) with \cry few higji reduction in sedimentation. Control by domical and bulbous forms. For the loosely substrate-type inadditiontosedimentationrateis hound, frameslone and covcistone style ofp indicated, with growth forms reducing their & reefsthese shapescanbeattributedtotheneedfor weight perunitarea(Kershaw. 1984; Bjerstedt the stromatoporoid to grow mote quickly Fc-ldmann. 19X5; Kershaw. 1990). Some ofthe laterallythan vertically across a muddy substrate laminar forms in these occurrences are for support, thus distributing the weight aero spectacularly thin in comparison to their width larger surface area. This phenomenon has been [Fig- 3). St Jean (Iu71) suggested thai thin d by several authors (Meyer. 1981; Bjerstedt laminar forms occurred in oxygen poor $ Feldmann. 19K5; Fagersuom, 1987; Kano, conditions- but as Bjerstedt & Feldniann (1985) 1990). The strategy was called the 'snow-shoe' have argued, a laminar form would be at a approach by Bjerstedt & I'eldmann (1985), uage in such circumstances with the Within the 'rauk' patch reels the stromatoporoid living surface close to the sediment-water dsokemliectaolnsforamres,ibnudtitvhiediuraslulpyerdpoomsiitniaotnecdreahtvesltohwe biniotteurrbfaatcieon., Fanudrtthheerpmroerseen,cetohfemoelxlutsecnssiavned relie! profile oi the patch reef. Away from brachiopods suggest a moderately wcil- ihescpatchreefs andcommonIv inli i itotfljd o\ygenated benthos at L803. them, dendroid, mostly stachyodiform elements ofthe fauna are common. Robustly dendroid .skeletons ate abundant in rgoonal pavement facies. attesting to the STROMATOPOROID SHAPF WITHIN ii mportance of the dendroid form in mud- LAGOONAL PAVEMENTS. A number of dominated substrates. Bjerstedt & Feldmann eoverstonc occurrences were interpreted as vo) argued that fasciculate skeletons are lagoonal pavements either leeward ot biuherms disadvantaged within this environment. Clearly Ot vviihin a biostfomal complex (eoverstonc die abund Fd fdraJd forms within the Stibi'acies (Cook, 1995)). These pavements are muddy facies of (he Rurdekin Formation refutes almost exclusively composed of laminar to very- thisargument.Onthecontrary,dendroidskeletons low domical stromatoporoids (Fig, 3). Skeleton wouldbeabletriraisethelivingsurfacewellabove edge raggedness suggests moderate the sediment waterinterface. The only problem is nFROMATOPOROIDS FROM II IJ PANNING RIVER GROUP 469 The dominant (>7>%) gross skeletal shape is irregular, consisting of many compound forms with laminarandhighdomicalcomponentstothe one skeletal wlit. Others are multiply bulbous, arising from a low domical form. Of the 63 skeletons assessed in this biostrome only 48 could be assigned confidently to an approximate skeletal shapecategory(Fig.4)andthesizeofthe skeletons is highly variable. Unfortunately do»moiwcal dhoimghcal bulbous preservation is very poor, with much skeletal silici fication. neottiorphtgni and minor FIG. 4. Histogram showing pn.portions of 2 dolomitisation, rendering the taxonomy of this 1 eietal shapes for compound skeletons from faunule difficult The skeletons present are quite biostrome within IbssihTerous siltstane Packs at distinct from others in the Burdekin succession. no\imatel\ !6tt1 above base ofsection. I he majority are compound, composed of repealed, variably thin layers of encrusting to provide a substrate upon which to initially organismsincludingstromatoporoids,al\colilids colonise, but the abundant small bioclasts of and algae (see below). Their compound nature mollusean hash, small eorals and other may explain the aberrant growth forms of the millimetre-scale debris would have been sufficient. As sedimentation progressed, the skeletons. Ifa single taxon adopted a limited and related range ofgrowth forms (see below), then dendroid skeleton, becoming progressively more the superposition ofmany taxa in an encrusting buried in the substrate, would gain stability. relationship may be expected toproducea highly STROMATOPOROFD SHAPE WITHIN irregular form Thus 'he skeletal form of most BTOSTROMAL OCCURRENCES. Several individual taxa within this biostrome is laminar, types of biostrome were identified by fades with thin encrustations complexly overgrown to analysis in Cook 1995). These are generally the form irregular compound skeletons. Away Ifom, { innermost shelf biostrornes of the rossili&rouB and within, the biostrome dendroid (mostly sfltstonefeciestypically representedat L788, and tabulate coral) skeletons are very common the extensive proximal shelf biostrornes (2) Proximal shelfbiostrome. represented throughout the Fanning R. area. Innershelf biostrome I i ) (JCUL788) Study of this biostrome a revealed thai it was loosely bound. enclosed by "W=57 dominantly silioiclastic laeies, and formed in a shallow, Bubtida] environment, situated ''J««•w.j«: extremely close to shore in a restricted embayment With a moderate sedimentation rate as suggested by the sandy -:! stringersand interbeds. Inmany 4D ways ihis small biostrorua! lens, and the overlying 3 metres of stromatoporoid- bearingsequence, isoneofthe '..:> BD most instructive in the 6cB(uu1rrsdaeinkndianf7se0ecqi%eusenswciieltsihciabcseltiatwseolecin-e I f\<ac>.ie5.sSotfrothmeatBouprodreokiidnskFeolremtaaltimoonr,phBoivlaorgiyatferoplmotprsohxoiwmialngshveelrftibciaolsihreoimgahlt component (determined by ih\ei\gvhetr(eVu),bbaasa\l\ywiiddtthh(BB))ianncdendtiiamgeotnraels,diisrtiaanncgeutIaPr)plfootltloiwhionvgtinhgemveerttihcoadl ( bulk acid dissolution of ofKfifthaw & Riding) 1978). with diagonal angle sei at 25° A. L7SS 26m several samples). e base, I »ove base. 470 MEMOIRS OF THE QUEENSLAND MUSEUM Stromatoporoids from the proximal shelf biostrotnal facies at L788 show a wide range ofshapes and sizes, but with a general dominance of low to high domical forms, L781/2 sporadic bulbous forms, and a 30 60 90 120 15 lower proportion of laminar B S0! n=Z7 ' _ : forms (Fig. 5) in comparison 40- to the inner shelf. Compound V30- • skeletal phenomena are much 20- nleusmsbceormsmoofn.frTahgemreentaarle lsakregle- F100--. . -•". " S - . " . , 1 L779, a etal remains within reworked cm ufancrieeswboutrkiteids obvfiaocuisetshattdhoe FIG. 6. Stromatoporoid skeletal morphology from proximal shelf framestonefaciesoftheBurdekinFormation.A,verticalheight(V)versus represent the stromatoporoid basal width(B) in centimetres forL781/2 and L779. B, triangularplots of populations adequately. vertical height(V),basal width(B)anddiagonaldistance(D)followingthe Of the larger stromato- methodofKershaw& Riding (1978), with diagonal angle setat25°. poroid skeletons, many show directional growth changes, probably the result STROMATOPOROID SHAPE WITHIN ofin vivo reorientation. The marked dominance BIOHERMS (REEFS). Well exposed outcrops of higher forms in some units of the micritic of stromatoporoid framestone along the stromatoporoid floatstone (Fig. 5) may indicate Burdekin R. (L779, L781, L782) allow for a lower sedimentation rate, or a slightly reduced sizeable analysis of stromatoporoid shape ambient energy (turbulence) away from domains. The bioherm is dominated by low to shoreline. Bioturbation and the abundance of mediumdomical forms(Fig. 6),manywiderthan brachiopods negate low oxygen conditions. lm, and higher than 50cm. There is a general Sufficiently low energy ambient conditions reduction in the number of high domical and coupled with a lower sedimentation rate on the bulbous forms in comparison to the biostromal mid-shelfwouldhaveenabledhigherformstobe facies in the Fanning R. area which may be a maintained on the substrate. Inability of some functionofhigher energy at the reeftop, andthe higher stromatoporoid skeletons to maintain a general difference in the stromatoporoid taxa foothold may account for all the regrown high between the 2 areas. Whilst common, the domical stromatoporoids in the facies with dendroid fauna is less abundantthan in flanking reorientation due to sporadic toppling. environments, restricted to interskeletal niches. Interstitial stachyodiform and amphiporiform STROMATOPOROID SHAPE WITHIN taxa play a major role in the biostromes, with DISPERSED STROMATOPOROID PAVE- Amphipora dominating the muddy substrate, MENTS AND OFFSHORE THICKETS. These occupying patches between the larger stromato- environments were completely dominated by poroids. In addition Stachyodes costulata is Amphipora and/or ramose tabulate coral taxa, found as detached branches and as branches andtheroleofthenon-dendroidstromatoporoids originating from an encrusting surface, dem- was minor on the distal shelf. Growth form was onstrating change in growth form within the one variable, with some facies dominated by thick skeleton. There are no recorded attachment or laminar and low domical forms (Fig. 7), both encrustationhabitsofAmphipora. Perhapsthis is with and without ragged margins, and other a function of a small size of the attachment occurrences showing sporadicmedium and even surfaceorperhapsthemethod ofattachmentwas high domical forms. The thick laminar and low purely soft-part, but the latter possibility seems domical forms occur in the dispersed unlikely given the ability oiEuryamphipora to stromatoporoid packstone facies which, given encrust. Both dendroid taxa were successful the abundance of micrite presumably derived between the larger stromatoporoid skeletons from algae, wouldhavebeenahighlyproductive where they were sheltered, and able to raise the carbonate factorywherecarbonateaccumulation livingtissue well above the substrate. was relatively high, the overall substrate STROMATOPOROIDS FROM THE FANNING RfVER GROl ': 471 substrate, \sthe number ot large skeletons increased, the skeletal substrate available |0 for colonisation was enhanced, increasing Q 80+ the potential lor lrame-building. Thus the 50 transition from laminar to domical •". 10 dominant facies reflects the development 2Q from £LH encrusting pavement to a framework. A reduction is sedimentation rate is possible, but would have been affected by the development of a framework and the consequent elevated growth form ofthe reefsurface from the surrounding substrate. Any change in rii., ?. st'omatoijotoid Bket from disperse turbulence would also result primarily stromatoporoidand corallinepackstone raciesoftheBurdckin Formation Bivariaie plot shows vertical height <\') versus from reef growth, rather than vtca versa. basalW;id(Vtih,(Bb)asiaplcewntiidmtehtre(sB.) Iaini'diimduiiaagropnlaoltssdihsotManc'efl(iD9) Tchhuansgteheismasjuobrstrcaontteroalvaoinlabfinloirtpyholwoith a following the method of Kershaw & Riding (1978), with feedback relationship between substrate diagonal anglesetat 25°, L781 units abovehamestoncfacies. and skeletal morphology. relatively soft, but with much millimetre-scale FANNING RIVER CAVES. Brief skeletal debris available on which to initially mention hasalready been made inCook( 1995)of encrust. Sporadically preserved raggedness the sequence exposed in fanning R. C; within bjghef fbtms ol'lhe coralline packsione (L803). The sequence is interpreted as a waning faciesSUggestSthat theseskeletonskepipace with cycle commencing with a boulder rudstone vo^: carbonate accumulation following initial rapid composed entirely o\' teworked skeletons, an lateral growlb. upper boulder rudstone with occasional in situ skeletons, a shingle zone with pebbk- STROMATOPOROID SHAPE WITHIN eobblc-sized reworked skeletons and many v SILTSTONE MFCROATOLLS. Many situ skeletons with ragged margins, and an upper stromatoporoids within this facies arc encrusting wackestone-coverstonc /one dominated by mhabil. thushavinga laminarform,buttherearea extreme laminar forms.The shape progression in few low to medium domical forms, and sporadic theupper3 zones(Fig, 9)showsareduction in the high domical forms. ClathrocoifaflQ spiSSQhas an profiles of stromatoporoid skeletons mirroring irregular, laminar shape in this facies. Saldireila the reductionin coarse skeletal debris, and hence buechetfensis and Stromatopora kuepschii show hydrodynamic energy. Collection ofmaterial for low to medium, rarelj high, domical skeletons. taxonomic analysts was notpossibleas the eaves The varying mtcroenvnonmcnls around such areenvironmentallysensitive. Howeveritisclear EthhphyHttm accumulations would account for much morphological variation, and the laminar encrusting habit) forms would result from strong t competition lor substrate control within an increasingly clastic environment. SHAPFZONATION BURDEK1NRIVER,Laminar formsinthecover- stone facies of L779, and L7S1/2 arc vertically succeeded by low-medium domical forms ofthe bjohenn facies. This vertical zonationjs strikingly obvious (Fig. 8) and cannot be related to fauna I differences as the stromatoporoid tu\a are common to both iacies and dominated by Hcrmaiosiroma mocuhUum and Gemmostroina hendcrsoni. The progression is interpreted as one FIG, 8, Stromatoporoid shape domains using VBD ofself-generatingchange in the available skeletal triplot forcover&tonc to hrarnestone facies I ": ' 1 . 472 MEMOIRS OF Mir QUEENSLAND MUSEUM I domical in coverstone fades. 75T Similarly Hermntostrnma r.;.\ fnaatlatitm is laminar in 1'- e v coverstone facies and low- 30-- medium domical in the 15-- biolicrma! complex. Sometaxa a 2 40 SO 80 130 120 140 16Q 1430 20!0 2210 display a wide range ofgrowth 75 B forms, from laminartobulbous and irregular within the same a^ facies. Sntr/ivuies COStulata I had coexistent laminar, 15 silly HoatstOffe irregular and stacbyodiform Q -i a BD B efl .in 1so 1sio aa1o 2210 fgrroowmtha,ninedniccartuisntgintghatsuitrafraocsee. rQ Other taxa such as Hermato- StKOiwQ episcopal^ strongly 30 restricted to particular facies, i05^ —20 *1o ea! »— 100 120 140 1-6rltuo0bwbelrIySs1tOriilfoia2gtl0s»et0ainos2p.e210 aslrhocawpaeldm(olomasmiticnaeaxlrc),l.ulessiGsvieclvoyemnmoofntohlnayei 75 B 50+ individual taxa display a range of shapes across, and within, I5 V specific environments, these 15 upperrbdstone data show there is very weak D geneticcontrolinadditiontoen- 20 40 50 ao 100 120 140 160 130 200 220 vironmental controls outlined 75j s below -.,0 45-. CONTROLS ON SHAPE The nature of the muddy 04 20 40 BO 30 1Ban iza 140 ISO 180 200 220 msuebnsttartatieonanwderthee frualnedao\m'ensetdail- determinants of skeletal shape within the inner shelf. FIG. 9s Stromatoporoid shape change fur measured section in Fanning RiverCavesL803demonstrated in grossskeletalshapeplots foreachunit Progression fromlaminarforms (coverstoneat top). to low domical forms rellected in the transition from lagoonal from field inspection thai there was no obvious pavement to bioherm was controlled by the change in the faunal constituents. The obvious increasing availability ofskeletal substrate. In the change in gross skeletal shape demonstrates that biostromal complex, innermost dwellers hadtheir here decreasing energy favours lower skeletal irregular ^hapc controlled by the sedimentation profiles. Bioturbation rules out the possibility o( pattern, the encrusting strategy of the dominant an oxygen-poor substrate and the thin forms can lavaandthedominanceofskeletalsubstrate. Inthe be attributed to moderate rates ofsedimentation proximal shelf biostromc higher skeletal farm which periodically smothered the organisms, rellected thequietambientconditions, sponsoring some toppling and re-growth. STROMATOPOROID SHAPE AM) I OVERGROWTH RELATIONSHIPS Strotnatoporoid taxa within the Fanning R. Group display a range of shapes lor individual Although encrustation of individual taxa(Fig. 10). Most taxa. ofwhich <7 hemiei sttomatoporoid skeletons by other stromatoporoids is an example, are restricted to the low domical and a range of other organisms is common, Chfi and adjacent growth tonus. (_/, hctiJc/suni is low phenomenon has been given little direct attention to medium domical in form within the biohcrm (Kazmiercyak. 1971; Neild. 1986; I agcrstrom, and hiostromes, but is laminar to very low Ic>87, May 1993k although numerousauthorshave