Brachiopod-Bivalve Assemblages of the Middle Triassic Terebratula Beds, Upper Silesia, Poland

Home , Plagiostoma (bivalve), Terebratula

Brachiopod-bivalve assemblages of the Middle Triassic Terebratula Beds, Upper Silesia, Poland

ANDRZEJKAIM

Kaim, A. 1997. Brachiopod-bivalve assemblages of the Middle Triassic Terebratula Beds, Upper Silesi4 Poland. - Acta Palaeontologica Polonica 42,2' 333-j59.

Five types of brachiopod-bivalve assemblagesoccur in Terebratula Beds and in the lower part of the Karchowice Beds (Middle Tiiassic, Muschelkalk) from the StrzelceOpolskie Quarry (Upper Silesia). These are: (1) Brachiopod coquina Assemblage dominated by the terebratulid brachiopod Coenothyris vulgaris; (2) crumpled/wavy Limestone Assemblage including bivalves and brachiopods; (3) Bivalve coquina Assemblage dominated by pseudocorbulid bivalves; (4) Hmdground Assemblage dominated by the brachiopod Tetractinella trigonella; and (5) Crinoid Limestone Assemblage dominated by crinoid columnals and the brachiopod Punctospirellafragilis. The distribution of the assemblages correlates with the eustatically-controlled lithological vmiation in the carbonate-dominatedsequence of the Upper Silesian Muschelkalk. The brachiopod coquinas are parautochtonous remnants of terebratulid banks which thrived during the high bioproductivity but low oxygen conditions. Those conditions were caused by the biogenic influx generated from the terrains flooded during the Middle Triassic transgression. During the regressive phase, that resulted in the gradual decreasein bioproductivity and parallel increase in oxygen levels, the Grebratulid banks were replaced by pseudocorbulid banks. With the further regression - and thus, the further increase in oxygen level - pseudocorbulid banks were replaced by the assemblagesindicative of well-oxygenated oligotrophic environments (Hardground and Crinoid Limestone Assemblages). The observed changes in the faunal composition reflect mainly differences in metabolism and feeding strategy among dominant taxa.

Key words: Paleoecology,benthic assemblages,brachiopods, bivalves, Muschel- kalk, Triassic, Upper Silesia, Poland.

Andrzej Kaim [[email protected]], Instytut Paleobiologii PAN, ul. Twarda 5l/55' PL00-8 I 8 Warszawa,P oland.

Introduction

The TerebratulaBeds in the Muschelkalk (Middle Triassic) sequenceof Upper Silesia (Figs 1, 2) have been known for their rich fossil content for a long time (Terebratula- Encrinus beds of Eck 1863, 1865). The first monographictreatment of the fossils 334 Triass ic brachiopod-biv alve ass emblages: KAIM

Ei.Tllt"oig"-os.marine andcontinental facies ffi carbonatefacies -l Alpmerealm raMuschelkalkoutcrops

:^ -rI] :LreTaceous t-. . . . I UPPerlnasslc Far+H Muschelkalk fault F llltowertriassic ffiPareozoic ./

Fig. I A. Middle Triassicpaleogeography of Poland.Modified afterDzik & Trammer(1980). B. Geological sketchmap of the westempart of Upper Silesia.Modified after Bodzioch(1993). occuring in this unit was publishedby Assmann(1937, 1944).He establishedalso a lithostratigraphicscheme which remains valid for this area to this day (Fig. 2). Subsequently,paleontological investigations supplied information about conodonts (Zawidzka 1975),foraminifers (Gufldzickt et al. 1975), and echinoderms(Hagdorn & Gtuchowski1995). Brachiopods were describedby usnarska-Tarerzak(1988, 1990). ACTA PALAEONTOLOGICA POLOMCA (42) (2) 335

x .p Depth curve Sequence Depositional Lithology and (afterSzulc 1993) Stratigraphy Environment Lithostratigraphy relative of the Silesian o H;* q ts B.i shallowing (afterSalc 1993) Muschelkalk b..x6 (a@ordingto Asslrrm 1944 <- 00 6 F E: md Szulc1993) ------> (afterSzulc 1993) U) U) CAN SF rI deepening ---# Keupr Redbeds I LST 6 a Bfisroffi Coastal sabkha atavus f, Beds I{ST to ercdis tmer Wilkowice Restricted nmp ffi Beds %) mid TST 4+ Tamowice Restrictedinner Middle <--f-'r- Beds ranp 3 Muschelkalk Interval ffi Diplopom I-sT Judtcantes Midramp Beds and 7H Neoschizod.us orbicularis '-s2aY. Patch reef belt of Karchowie mid/outer ramp ffi Beds Decurtella g$- Fere@{a s9ry :r16 fffffi Wt Euls : i 141: :E o Skeleal shoal G6rudi.e of outer Erp Beds TST Open outernmp

Myophoria -:# tsT vulgais, =w Imerramp Beneckeia .y_s:.... buchi Open, mid and Gogolin ramp Dadocrinus wH Beds i -)4t4 TST b Restricted B = imer ramp I c Ytg/- ffi -*TtT*8 Ritt Coastal sabkha I-ST

spongebiohem (l cabmusmdshoals @evaporites @dotomltes ffirgilites Ecalcilutites/calcisiltites F

calcaenites period of high bioproductivitY m defmed sets @oolltes ffi coml biohem flshallow-water

Fig. 2. Stratigraphy and evolution of the Silesian Muschelkalk Basin. After Szulc (1993) and Hagdorn & Gluchowski(1993).

Of special interest, due to their mass appearance,arc the terebratulids, particularly Co enothy ris vulgaris (Sclrlotheim,1 S20) (Malkowski 1975 ; Usnarska-Talerzak1988 ; Trammer et at. 1996).According to sedimentologicalinvestigations (D2ulyriski & Kubicz 1975;Bodzioch 1985;Szulc 1993;NiedZwiedzki 1993), terebratulid coquinas were catastrophicin origin; an effect ofstorms.and,/ortectonic events.In contrast,little has been published on paleoecologyof the fossil assemblagesrepresented in the TerebratulaBeds. This paper,based on the field observationsand quantativedata from the SfizelceOpolskie Quarry, aims at a detailedpaleoecological analysis of brachiopod andbivalve dominatedassemblages of the TerebratulaBeds. 336 Triassic brachiopod-bivalve assemblager.' KAIM

"wl'- F{ heap []l'l Diplopora md Karchowice Beds ffi TerebranrlaBeds ffi c6raZdre Beds ffi GogolinBeds - quary walls ,ry w publicroads -'fault ."*i x*re quarry roads lD water reseryoirs

Fig. 3. Geologicalsketch map ofthe StrzelceOpolskie Quarry showinglocation ofthe sections(see also Figs 4-9).

General setting and methods

The StrzelceOpolskie Quarry provides one of the bestexposures of the Muschelkalk depositsin Upper silesia (Fig. 1). Paleogeographically,this is the sourhernmargin of the GermanicBasin. The MuschelkalkSea was connected with the TethysOcean to the south. According to Szulc (1993), the TerebratulaBeds representthe maximum transgressionevent in the Silesianpafi of the MuschelkalkBasin (Fig. 2). In the first stepof my analysis,I divided the sectioninto distinct,environmentally- dependentlithologic units and determinedtaxonomic composition of their fossil content.In the secondstep, I conductedthe taphonomicand quantitativeanalyses of ACTA PALAEONTOLOGICAPOLONICA (42) (2) )J I

m 17.0 I "tuy |-i;F orgmodetritallimestone

F-l-lll limestone o ".;1e;6 16.0 ffil crumnledlimestone ffil brachiopodcoquina { SectionC 15.0 ffi wavylimestone o FI ElJlll recrystalizedgrainstone @,r.0 ffil micriticlimestone 14.0 FT fi{ffi bivalve coquina N-Z trace fossils 13.0

SectionB SectionE l 1.0 6 10.0

9.0 9.0 ! SectionD 8.0 8.0

SectionA 7.0 7.0

til {n ft q,

€D BrachiopodCoquina Assemblage O BivalveCoquina Assemblage d:'f;$ crumpled/Wavy LimestoneAssemblage .{:} HardgroundAssemblage GOF.AZDZE BEDS @ CrinoidLimestone Assemblage

Fig. 4. Five measuedsections from the StrzelceOpolskie Quarry andthe stratigraphicdistribution of the fossil assemblages.Abbreviations: FM - firmground,CV - bed with unusuallywell preservedspecimens of Coenothyrisvulgaris (Schlotheim,1820). 338 Trias sic brachiopod-biv alve ass emblages.' KAIM

uS 'id%ts F ci ! u -3S:"G';BSrt"X ! SR!sac .='{E SectionA SsESss;3 S S I T

--- rI

rrl

f ffi1.*.pledlimestoneW*unylimestone "tuy crin oi d Ii mesrone j'i--llll brach i F::r l-:' :::fl :::k"' ffi opodcoq ui na

N-Z tracefossils

Fig. 5. SectionA of the StrzelceOpolskie Quarry andstratigraphic ranges ofthe mostcharacteristic fossils. Bars show relativeabundance of calcitic brachiopodand bivalve shellson the beddingplanes. A, B. Bra- chiopodcoquina assemblages. the fossils in each unit and distinguishedfossil assemblages.Finally, I offered pa- leoecologicaland paleoenvironmental interpretation for thoseassemblages. I obtained data for paleoecologicanalysis by counting specimensin the field, primarily on bedding planes.In addition, to estimatebiovolume (as an approximation for biomass),I measuredarea covered by eachspecimen (cl Fiirsich & WernerI99I). Becausethe taxonomiccomposition of autochtonousand parautochtonousshell beds does not differ from the composition of the much morc heavily time-averaged, multiple-eventshell beds, the latterhave not beenexcluded from the analysis.As long as environmental parameterswere constant,time-averaging influenced only the total abundanceof specimensbut not necessarilythe relativeproportion of speciesor the taxonomicdiversity (Fiirsich& Aberhan1990). The recurring faunistic associationsare referred to here as 'assemblages'.This neutralterm implies purely descriptivestatus of the units. Dependingon their tapho- ACTA PALAEONTOLOGICAPOLONICA (42) (2) 339

s ss * 3S EF 8E gG S - 6S- e P.F q i : st'u* ! IE"-* SectionB .d ttst.SsRFFfs$ssStiEssB;xt.d C. vulgaris ssssssFE$$sso r I I ll I A Pseudolinrea sp. C. vulgaris E. dffirme

rII

II Plagiostoma sp. Myophoria sp.

IIT

I I I r r l------

l---l E. diffornte

T;D P. ernesti ffi ..'npled lirnestoneffi *rtry limestone f "tuy N. noetlingi llllTl limestoneffi micriticlimeston" ffi b.uchiopodcoquina ".i'oid

Fig. 6. SectionB of the StrzelceOpolskie Quany andstratigraphic ranges of themost characteristicfossils. Bars show relative abundanceof calcitic brachiopodand bivalve shellson the beddingplanes. A-D. Bra- chiopodcoquina assemblages.

nomic history and their temporal resolution, the fossil assemblagescan be interpreted ecologically to various extent and with various confidence(e.g., Hoffman 1979, I982a, b; Kidwell & Bosence1991).

Lithologic Units

The paleoecologicanalysis is basedon five sectionsfrom the StrzelceOpolskie Quarry (Fig. 3). The five sectionscover the entire span of the TerebratulaBeds and the lowermost part of the Karchowice Beds (Figs 4-9). Following Kotlicki & Radek (1975),I subdividedthe TerebratulaBeds into threeunits. The fourth sampledunit is the lowermostpart of the KarchowiceBeds (Fig. a) as definedby Bodzioch (1990). The four units can be brieflv summarizedas follows: 340 Triassic brachiopod-biv alve assemblages.' KAIM

s SF .FS E S E.".:$ !S A $a !.5,'€';h E**N.*t is t: *s{grs:^ Section C Sr*t8F ssss:seT e i3s i'^ ss sNssfi{ ssssssEF;s IT lateral changes

H. socialis II

Pseudolimeasp.J I ^ Plugiostomasp. Myophoriu sp.J C vulgaris p. ll. IPseudocorbLlusp. cf.pruecursor rl I lll--*----

P. regularis llt.lllt[ g,g!!! crumpledlimeston" ffi wavylimestone ffil organodetritallimestone r---r-a-ri @ brachiopodcoquin" flil]llllTlflf]lllbivalve coquina F]l micriticlimestone t- - -'-l crinoidlimestone l\-Z tracefossils

Fig. 7. SectionC of the StrzelceOpolskie Quarry andstratigraphic ranges of the mostcharacteristic fossils. Bars show relative abundanceof calcitic brachiopodand bivalve shellson the beddingplanes. A-C. Bra- chiopodcoquina assemblages. D. Bivalve coquinaassemblage.

Lower marls. - crumpled and wavy limestones dominate in this unit. Shelly fossilsare practically absent. Only in oneplace badly preserved tiny bivalveshave been observed(maybe Pseudocorbulasp.).In the upper part of the unit, in a layer of crumpledlimestone, a specimenof ammonitehas been collected. This specimenis very similar to Acrochordicerascf. ippeni (Arthaber,1880) described by Dzik (1990);the latter probably came from the samestratum. Crinoid limestone. - Two firmgrounds occur in the lower part of this unit. The middle and upper parts are composedof thick calcareniticbeds. Dominant skeletal components change upward from mixed skeletal debris in the lower part, through crinoid columnals in the middle part, to terebratulid shell debris in the upper part. This is consistentwith observationsof Szulc (1991, 1993),who also interpretedthis thick calcareniticlayer as tsunamite. ACTA PALAEONTOLOGICA POLONICA (42) (2) 341

ca .3S E F $tE $F € iR i b iB ^c Section D sSs i Es I - * si$sss$€€ ; r=-!. I lr l. r

:::I II il

clav wavylimestone ! E--:g:---"rT..?;il'lt# W recrysta I ized ffi I organodetri taI ;1-l-TTl brach i o pod T: :ij-Ij-Il :limestone ucoquina 4 gralnstone Ea-li,'#."r',|". Fl-Ztracefossils

Fig. 8. SectionD of the StrzelceOpolskie Quarry and stratigraphic ranges of the most characteristicfossils.

Coquinas and wayy limestone.- Four lithological types have been distin- guished: (a) Brachiopodcoquina. Up to 30 cm thick coquinalayers, separated by crumpled and wavy limestone,occur in the whole unit (Fig. 4). They commonly consistof the 342 Trinss ic brachiopod-biv alve ass emblages.' KAIM

'ti

\-F Section E .h\\": G* al ln t7.0' .cA

16.0.

T. trigonella 15.0' TT C, vulgaris t4.0. 4jfforme- P. cf . praecursor socialis I T. trigonella

13.0. I I S o.d. S4@ 12.0. I {E* ^. .: ii a EoX s; -l\ t- - - -l ffi.f crumpledlimesrone ffi*ury limestone1-:--:--:--:l crinoid limestone F;l micriticlimestone illlllilflffllll-llbiuul,'ecoquina l\-7I tracefossils

Fig. 9. SectionE of the StrzelceOpolskie Quany andstratigraphic ranges of themost characteristicfossils. Bars show relative abundanceof calcitic brachiopodand bivalve shellson the beddingplanes. A. Hard- groundassemblage. B. Bivalve coquinaassemblage.

mixture of brachiopod and bivalve shells (articulated and disarticulated), shell frag- ments,crinoid columnalsand echinoidspines. (b) Crumpled and wavy limestone. Limestone beds which exhibit deformational sfiucturesvarying from wavy bedding and gentle undulations,to structuresintricately crumpled and fragmented(for more details see Bogacz et al. 1968). Fossils are uncommonbut their number increasesupward. (c) Bivalve coquina. This litology appearsin the uppermostpart of the unit as thin shell bedscomposed of closelypacked internal molds of small articulatedbivalves. (d) Organodetrital limestone with foraminifers. Numerous benthic foraminifers, chiefly Glomospiradensa (Pantid, 1965), are the main componentof this limestone. The thin sectionanalysis suggests that this is a microfaciesanalogous to that described by Glazeket al. (1973). Unit IV/A of the Karchowice Beds sersa Bodzioch (1990).- Crinoid andmicritic limestones(pelmicrite according to Bodzioch 1990)dominate in this unit. C. vulgaris and ACTA PALAEONTOLOGICA POLONICA (42) (2) 343

E. dffirme, which are typical of the TerebratulaBeds, disappear.I identified sponges Silesiasponginrimosa Pisera & Bodzioch,1991, as well as brachiopodsPunctospirella fragilis (Sctrlotheim,1814) and Tetractinellatrigonelln (Schlotheim, 1820). Very numerous ile columnalsof crinoids and,in places,shells of unidentifiedbivalves.Hardgrounds with a rich assemblageof frace fossils are well developedon the micritic limestone beddingplanes (see Bodzioch1994 for description).

Description and interpretation of the fossil assemblages

Brachiopod CoquinaAssemblage. - 38 beddingplanes with 1598specimens were classifiedas brachiopodcoquinas. I indentified ffieen speciesof bivalves and brachiopods@ig. 10).Two species,Coenothyris vulgaris (Schlotheim, 1820) andEnantiostreon difforme (Schlotheim, 1823) make up nearly 907oof fauna-The two speciesare dominated by large, most likely adult, individuals. Rhynchonellids Decurtelln decurtella (Girmd, 1843)and spiriferidsHirsutelln hirsuta (Alberti, 1865)are also characteristicof the BrachiopodCoquina Assemblage(Fig. 11B, C). In placesother fossils appear including: Plagiostomacf . striatum (Schlotheim,1823), Pseudalimea acutecostata (As- smann, 1937),Pseu&tlimea sp.,Hoernesia socinlis (Schlotheim, 1823),Prospondylus comtus(Goldfuss, 1826) andProspondylus ernesti Assmann,1937 , and?Leptocfuindria sp. Columnals of crinoids and spinesof the echinoid Triadotiaris grandaeva (Alberti, 1834)occur sparsely. I distinguishedtwo main types of coquinas.The coquinasof the first type are composedof articulated shells of brachiopodsand epifaunal bivalves, often presewed in life position.The valvesare fragmented only rarely,signs of abrasionand bioerosion are rare, but encrustationis present.Thus, thesecoquinas are regardedas autochthonous. It is hard to find them in the quarry wall, but they can be observedon the loose blockson the quarryfloor (fourbeddingplanes; Fig. 11A).The coquinasofthe second type consistof closely packed,commonly disarticulated,low to highly fragmented valves, and exhibit a sharp erosive base. These non-autochtonousshell.beds are, according to Bodzioch (1985), single or composite tempestites(one-event and multiple-eventbeds sensu Aigneret al. 1978).Both types of coquinasshow similar taxonomiccbmposition. Almost all animalsin the BrachiopodCoquina Assemblage represent sessile epibenthic organisms.Few exceptionsinclude the semi-infaunalbivalve Hoernesiasocialis and the vagile epibenthicechinoid Triadotiaris grandaeva.The most numerousbrachiopod Coenothyrisvulgaris hasa largepedicle foramenwhich suggeststhat it lived attachedto the substratewith its pedicle (for detaileddescription of attachmentscars see Malkowski 1975).These brachiopods could haveformed clusterswith many individuals sequentially attachedto oneanother, as canbe observedamong some Recentbrachiopods (e.g., Thayer 1975).Among othercommon organisms of the brachiopodcoquinas, the bivalve Enantio- streondifforme, that lived cementedto the substrate(Nolte 1989;Ockert 1993; Bodzioch 1994;Fig:11A),is alsonumerous. Crinoids and Newaagia noetlingi (Frech, 1909), that alsolived cementedto the substate,are also present. Abundant occurrence of E. dffirme strongly suggeststhe presenceof hard substrate.The absenceof fully infaunal organisms further corroboratesthat interpretation.In sum,the faunal compositionof the assemblage 344 Triass ic brachiop od-biv alve assemb lages.' KAIM

I\T]MBER AREA 0 50 lNTo 0 50 100To

Coenotlryris vulgais

Enantiostreon ffi@ difforme I ffiPlagiostoma sp.

Decurtella ffi @ decurtata

HirsutelLa H hirsuta

Ptmrtospirella w fragilis

,u*,,^"o,n. |

Hoemesia w socialis other bivalves and brachiopods

Otherfossils: crinoid columnals # & Triado t iai s g r andaeva spines Fig. 10. Relative abundanceof speciesin the Brachiopod Coquina Assemblageestimated by number of specimens(eft chart) and surfacecovered by them on the bedding plane (right chart); basedondata from all examined bedding planes. Shell drawings used in this and other diagrams taken frem Schmidt (1928) and Hagdorn& Gluchowski(1995).

suggeststhat the substrateinhabited by it was at least firmed. This preventedinfaunal organisms from entering the habitat and allowed, in turn, for the development of terebratulidbanks. According to Bodzioch (1985),the origin of thesebanks was similar to that of the terebratulidbanks from the Upper Muschelkalk of Germany(Aigner et al. 1978;Hagdom & Mundlos 1982). The Brachiopod Coquina Assemblage, with numerous large terebratulids and oyster-like terquemiidsEn antiostreon seems analogous to the oysterbank assemblages ACTA PALAEONTOLOGICAPOLONICA (42) (2) 345

,tl rj\.{,

t rt

Fig. 11. Brachiopod Coquina Assemblage. A. Bedding plane with autochthonous association of the brachiopod Coenothl,ris vulgaris (Schlotheim, 1820) andthe bivalve Enantiostreon difform.e (Schlotheim, 1823). The white arrow indicates Ihe Enantiostreon difforme specimen attached to the brachiopod Coeno- th1:ris vulgaris. Note that the bivalve shell is shaped according to the brachiopod's morphology; x 1.2 8, C. Ventral and dorsal valves of the brachiopod Hirsutella hirsuta (Alberti, 1865) from the brachiopod coquina fossil assemblages; x 2. 346 Triassic brachiopod-bivalve assemblages.' KAIM

NT]MBER AREA 0 50 100 Vo 0 50 lNTo

Coenotlryris vulgaris

ffil;ri:#"""

ffir;::;trr'*

Hoemesia ffi socialis

Fig. 12. Relative abundanceof speciesin the Crumpled/Wavy Limestone Assemblageestimated by number of specimens(left chart) and surfacecovered by them on the bedding plane (right chart); basedon datafrom all examined bedding planes. from the early Kimmeridgian of Poland, where the oyster Actinostreon gregareum (J. Sowerby,1816) and the terebratulid,Epithyris subsella(kymerie, 1846)predomi- nate (Dzik 1979). The zeilleriid brachiopods were rare in the early Kimmeridgian oyster assemblage(Dztk 1979) and in the Anisian brachiopodcoquinas (cl Usnarska- Talerzak 1990). These assemblageswere both most likely characteizedby eutrophic conditions (Machalski 1993; this paper). The zeilleriids seemrather to be typical of oligotrophic environments e.g., in the early Kimmeridgian oolite assemblage(Dzik 1979) andthe Anisian spongebioherms (cl Assmann 1937;Bodzioc,hl994). Crumpled/Wavy Limestone Assemblage. - This type of assemblageis representedby 110 specimenson three large bedding planes.Three speciesof bivalves (E dffirme, P. cf. lineatum,H. socialis)and one brachiopodspecies (C. vulgaris) ne present.C. vulgaris prevails in number (Fig. 12), whereasE. difforme andP lineatum prevail in covered area. Fossils are highly dispersed within the limestone. Large number of fossils have been observednear contact of the crumpled and wavy lime- stoneswith coquinas.The most typical speciesof this assemblageis the large bivalve P. cf. Iineatum,oftenpreserved in life position (seeSeilacher 1954). This type of assemblagehas'been observed within the crumpledlimestone and also in the wavy limestone.According to Bodzioch (1985) and Niedlwiedzkt (1992),the crumpling of limestone in the Srzelce opolskie Quarry was produced by infaunal organisms.Indeed, traces of activity of soft-bodied infauna are common in thosebeds. ACTA PALAEONTOLOGICAPOLONICA (42) (2) 347

Fig. 13. Bedding plane with bivalve coquina assemblageincluding Pseudocorbulasp., Enantiostreon difforme (Schlotheim,1823), and Plagiostoma cf . praecursor (Quenstedt,1856); x 1.5.

Such activity surely enhancedinstability and a density stratification effect. The trace fossils found here (Planolites andPalaeophycus accordrng to Szulc 1993) are com- pressedand smearedwhat is indicativeof soupyor soft bottom conditions(compare Ekdate 1985).It is noteworthy,that the C. vulgaris samplesanalyzed by Matkowski (1915) surely came from the crumpledlimestones (particularly from CV bed - see Fig. 4) wherethe brachiopodsare preserved very well: with completevalves and often evenwith their original color pattern.The unconsolidatedbottom forced the brachio- podsto utilize other shells(also of the samespecies) as a hard substrate.The semi-infaunal bakevelliid Hoernesiasocialis, that lived in soft-substratehabitats (McGhee 1978),is more commonhere than in any othertype of the assemblage. Bivalve CoquinaAssemblage.- Nine beddingplanes with697 specimensrepre- sentthis type of assemblage,which includesten speciesof bivalvesand brachiopods. The smallbivalve Pseudocorbulasp. is the dominantspecies (80Vo in number,47Vo in area;Fig. 14). Abundantare also other bivalves:Plagiostoma cf . praecursor (Quen- stedt,1856) (57o innumber, I57a inarea) and small individualsof E dffirme (57oin number,l57o in area).Only onebrachiopod species, C. vulgaris, is numerous(3Vo in number,l\Vo inarea).Less common areH. socialis,Plagiostoma sp. and Pseudolimea regularis (Alberti, 1864). Bivalve coquinasoccur as thin beds(up to few centimetresthick) or pavements. Pseudocorbulasp. is representedby internalmolds (Fig. 158, C) denselypacked and chaoticallyoriented on the beddingplanes (Fig. 13, 15A). Valves,before their dissol- ution, were articulatedand closed. Such a mode of preservationof infaunal, thin- 348 Trinss ic brachiopod-bivalv e assemblages.. KAIM

NT]MBER AREA 0 100Vo 0 50

Pseudocorbula sp.

Plagiostomn cf ffi ffi praecursor

Enantiostreon ffi ffi difforr* m Coenothyris ffi ffi vulgaris W!::x:'

--ffirusiono^orv.

H Pseudolimeo E regularis

I Decurtella I decurtata

Pseudolimeasp. I

Fig. 14' Relative abundance of species in the Bivalve Coquina Assemblage estimated by number of specimens(eft chart) and surface covered by them on the bedding plane (right chart); basedon data from all examinedbedding planes. shelled bivalves suggeststhat this assemblageis predominantlyparautochtonous (similar to storm wave concenfations describedby Fiirsich & oschmann rgg3). The Bivalve coquina Assemblage was dominated by the burrowing infaunal bivalves,Pseudocorbula sp., and P cf . praecursor.Epibenthic species were much less numerous.only the ubiquitousC. vulgaris andE.dffirme arecommon. However, the

Fig. 15. Bivalve Coquina Assemblage.A. Bedding plane with Pseudocorbula sp.,Plagiostoma praecursor (Quenstedf1856),andsmallspecimensofEnantiostreondiffonae(Schlotheim,1823);x1.7.B,C. Internal moldsof Pseudocorbulasp.;x l.B. . ='€aj'

,-r,ki; 350 Triass ic brachiopod-biv alve assemblages.' KAIM

NT]MBER AREA 0 50 0 50

ffi@ W"'ffi:n*'"

ffinasiostomasp.

sv. $rseudolimea B ^ 1',:::l;I:

Other fossils: crinoid columnals

Fig. 16. Relative abundanceof speciesin the Hardground Assemblageestimated by number of specimens (left chart) and surfacecovered by them on the bedding plane (right chart); basedon datafrom all examined bedding planes.

individuals of E. dffirme found here are much smaller than those found in the BrachiopodCoquina Assemblage. It is possiblethat therewas too little hard substrate for epibenthic organisms. Most likely, there was at least a thin layer of unlithified sediment that made it possible for a shallow-burrowing infauna to colonize the substrate.The mass occurrenceof parautochtonouspseudocorbulid shells (Figs 13, 15A) and their morphology suggestthat thesebivalves built banks similar to those made by corbulid bivalves in the Jurassic(Oschmann 1988a, b; Wgnall 1990), Tertiary,and Recent (Lewy & Samtleben1979). Hardground Assemblage.- Except one case (Fig. 4), the assemblagesrepre- sentingthis type havebeen found only in the loose blocks scatteredon the quarry floor. The most common fossil is T. trigonella (70vo in number, 50% in area; Fig. 16). Relatively common is also c. vulgaris. considerablyless common ne E. dffirme, Plagiostoma sp., Pseu.dolimeasp., and D. decurtata.The brachiopodr. trigonella appearsoften in small patchesof aboutten individualsof similar age(Fig. 17). Most of the shells havejoint valves, with the pedicle foramen directed toward the substrate. Thus, the HardgroundAssemblage is dominatedby in situ preservedspecimens. In addition, T, trigonella occurs abundantly,usually exceeding50 individuals per square meter, in thin layers of fine and well-sorted organodetrital limestone that cap the hardgroundsurfaces. Such layers have beenobserved in the unit IV/A of the Karchow- ice Beds. The individuals of Z tigonella have also beenobserved in the fiIl of the hardgroundhollows. ACTA PALAEONTOLOGICAPOLONICA (42) (2) 351

Fig. 17.Hardground Assemblage. A, C. Beddingplanes with TetractinellatrigoneLla (Schlotheim, 1820): A x 1.5,C x 1.3.B. Unusualspecimen of T.trigonella with five ribs;x 2.

The Hardground Assemblageis dominated by the brachiopodTetractinellatrigonella. Its mass appearance is always associated with the hardground surfaces. The occurrence of individuals of similar size in patches and with the pedicle foramen oriented toward the substrate suggests that they had short strong pedicles and the brooding ofthe larvae had been restricted (similarly to some Recent brachiopods - Thayer I97 5, 1977; Valentine & 352 Triassic brachiopod-bivalve assemblages.'KAIM

NI]MBER AREA 0 50 100 Vo 0 l0O Vo

Tbtractinella ffi trigonella Pbgiostomasp. F ffi ffi | ';:#/:*'" Otherfossils:

Fig. 18. Relative abundanceof speciesin the Crinoid LimestoneAssemblage estimated by number of specimens(left chart) and surface covered by them on the bedding plane (right chart).

Jablonski 1983). This athyrid brachiopodcollected its food in detritus-sortingcurrents associatedwith the formation of the hardground.Special adaptationsto such environments- expressedin hydrodynamicallyoptimized shapeof the shell, strong attachment 'early to the substrateand warning'protection (Rudwick 1965)- efficiently eliminated competitorsthat collectedfood in a similar way. The sparseoccurence of the cementing bivalve E. dffirme despite the favorable substrate,suggests that some other factors played important role in controlling distribution of this species. Crinoid Limestone Assemblage.- I have found only one bedding surfaceof reasonablesize that representsthis assemblage(Fig. 19).The assemblageoccurs as the discretelaminae of disarticulatedbrachiopod and bivalve shells within the crinoid limestoneof the KarchowiceBeds, and is similarto Tetractinella/Encrinusassociation describedby Bodzioch (1994). The main componentof the limestone are crinoid columnals.Among shelly fossils,P fragilis dominates(907o in numberas well as in area;Fig. 18). T. trigonella appearsin smallnumber. Bivalves arrerare,represented by Plagiostomasp. and Pseudolimeadunkeri (Assmann, 1937).Bodzioch (1994) ob- servedthat individuals of P fragilis attachedthemselves to other skeletons(sponges andlarge bivalves such as Plagiostoma or Pleuronectites).Ihave found only disarticulated valves that must have been transportedsome distance.Thus, their primary relationto the substratecannot be established. Detailed description of the Karchowice Beds was made by Bodzioch (1994). He found sponge- coral-echinoderm bioherms in the middle and upper parts of this unit (which were not analyzed by myself), and he described 43 bivalve and brachiopod species,fifteen gastropod speciesand many speciesof spongesand corals from the Kmchowice Beds. ACTA PALAEONTOLOGICAPOLONICA (42) (2) 353

Fig. 19. Crinoid Limestone Assemblage. A. Bedding plane with Punctospirella fragilis (Schlotheim, 1814), Tbtractinella trigonella (Schlotheim, I 820), and crinoid columnals; x 1.6. B. Ventral valve of P fragilis; x 1.5. 354 Trinssic brachiopod-biv alve assemblages: KAIM

Factors controlling distribution of Triassic shelly organisms

Numerous factors may control distribution of Recent and fossil assemblagesin- cluding salinity, temperature,climate, substrate,light, and depth of a basin. I would like to concentrateon two of them, i.e., oxygen contentand supply of nutrients,because they seemto be main factors confrolling the vertical dishibution of the fossil assemblages during the sedimentationof the TerebratulaBeds. In addition. sedimentationrate may have played an important role in the caseof the Brachiopod Coquina Assemblage and Crumpled/WavyLimestone Assemblage. The benthicassemblages described above show features ofvariable oxygensupply. Following the classic l classificationscheme of Rhoads& Morse (1971;seealso Byers 1977;savrdaetal. 1984;Tyson & Pearsonr99l;Etter 1995),the environmentsof the TerebratulaBeds may be arrangedaccording to increase of the oxygdn level during their sedimentation: 1. Anaerobic biofacies: no shelly fauna and laminated sediment (crumpled and wavy limestoneof the lower mmls'unit). 2. Dysaerobicbiofacies: no shelly fauna and bioturbatedsediment (firmgrounds of the unit of the crinoid limestone and part of wavy and crumpled limestonesfrom the coquinasand wavy limestone unit). 3. Aerobic biofacies:shelly faunaand bioturbatedsediment. Benthic assemblagesin this biofaciesmay havebeen a:ranged according to increaseofoxygen level: (a) Brachio- pod coquina Assemblageand crumpled/wavy LimestoneAssemblage (they probably differ in sedimentationrate); O) Bivalve coquina Assemblage;(c) HardgroundAssemb- lage, crinoid Limestone Assemblage,and sponge-coral-echinodermbioherms of the KarchowiceBeds. The sponge-coral-echinodermbioherms of the Kmchowice Beds mav also be classi- fied underpoint 3(c). The anaerobicconditions during the sedimentationof the TerebratulaBeds were previouslysuggested by D2ut5niski& Kubicz (1975)and Szulc (1991, r993).It seems likely that the oxygen deficient conditions were causedby a high bioproductivity of the basin in which sedimentsof the TerebratulaBedswere formed. The dependenceof brachiopodson colloidal and dissolvedorganic matter makesthem abundantmainly in high productivity zones(Mccammon 1969).In contrast,suspension-feerling bivalves (all bivalves found in the TerebratulaBeds), feed on phytoplankton and suspended organicparticles (e.g., cox 1969;steele-Petrovii 1979;Rhodes & Thayer 1991)and canflourish alsoin ecosystemswith lower productivity levels. Increasedproductivity is causedby high supply of nutrients to planktonic organisms. Theseare mainly phosphatesand nitrates carried out either from deeperocean regions by upwellings and/or from the land interior by rivers. In such zones of increasedproductivity, insufficient supply of oxygen that hampersdevelopment of the benthicorganisms is commonly(but not always)observed (Demaison & Moore 19s0). Similar anoxicphenomena were identified in thePaleozoic @owen et al. I974;Thayer 1974) as well as in the Mesozoic (Rhoadset al. 1972; Demaison& Moore 19g0; oschmann 1988a,b; wgnall 1990, 1994;Etter 1995).These events are frequent$ asSociatedwith marinetransgressions (Demaison & Moore 1930). ACTA PALAEONTOLOGICA POLOMCA (42) (2) 35s

Brachiopods,particularly those having punctae (such as coenothyrisvulgaris), are better adapiedto the poor oxygen environmentsthan many other marine organisms'It is usually-regardedthat bivalve mollusks overtook the ecologic nichesoccupied earlier by the Uractriopods,now a relic group (Steele-Petrovi(1979; but seealso Gould & iutto*uy 1980; Boucot 1986; Rosenzweig& McCord 1991).In some present-day environments,however, in particular those with decreasedor variable oxygen content and sufficiently developed hard substrate,brachiopods continue to dominate over bivalves.This is the case,for example,in the British Columbiafjords (Tunnicliffe & Wilson 1988).Their advantagesin suchenvironments include: (1) low metabolicrates, l0 to 50Voof the oxygen uptake of comparablegastropod and bivalve molluscs held in for long similar conditions Arrry it al. 1989);(2) the possibility to close their valves periods of time (Shumway I9S2); and (3) easy conversion to anaerobicmetabolism (Shum- ?fU**"tt 1977)or decreasingmetabolic rates and respiration by the punctae way 1982;Thayer 1986; but seeReindlet a\.1995). Punctae are also sites of the storage of metabolites(Curry et al.1989). The TerebratulaBeds were deposited during the maximum transgressionof the early Middle Triassicsea (Szulc 1993;Fig. 2). Transgressionsmay result in biogenic influx from newly flooded terrains. The biogenic influx, in turn, increasesbiogenic productivity, but may also causeoxygen depletion in marine environments(Demaison & Moore 1980). In the early Middle Triassic eustatic regressionphase, a distinct shallowing took high primary biologic pro- place-duction (Szulc i99t;. niog"ttic influx ceased,reducing the and, as a resuli the oxygen conditions improved. In that period, a better oxygenation of the soft muddy bottom allowed for the developmentof the pseudocor- UuiiOfa*s. Corbulid associationsfrom the English and French Kimmeridgian have beenattributed to similar episodicconditions (Oschmann 1988a, b; Wignall 1990)'The increasein oxygen content and decreasein bioproductivity both continued with the regression, whereas sedimentation shifted from marly to limy. Hardgrounds then developed with a mass occuffence of Tetractinella trigonell'a. That brachiopod was its Jurassichomeo- probably adaptedto lower productivity of ecosystem,similarly !o reef morph - Cieirothyris fleiriausa (d'Orbigny, 1850),which live.d in the coral enviionments(cf Malinowska 1965;Barczyk 1969;Wi6niewska-Zelichowska l97l). After the stabilization of the low sealevel and low productivity, as well as the increase in oxygen content, the sponge-coral-echinodermbioherms with numerousand diver- sified faunadeveloped (Bodzioch 1989,1991,1994; Pisera & Bodzioch 1991).

Conclusions

The brachiopod-bivalveassemblages in the Middle Triassic TerebratulaBeds from the the Strzelce Opotstie Quany, indicate profound changesin biological productivity of marine ecoiystem. They were probably evoked by a phosphateinflux from land areas newly flooded during the Early Middle Triassic transgression.The high primary biopioductior, oxygen -deficiency. In poorly oxygenated and nutrient rich "uur"d watlrs, the brachiopod Coenothyrisvulgaris characterizedby a low metabolic activity dominated.In transitional conditions,the small shallow-burrowing bivalve Pseudocor- 356 Triassic brachiopod-bivalve asssmgl6ges.. KAIM

bula sp. occurred,while in well-oxygenated,oligotrophic waters crinoids and the brachiopod Tetractinellq trigonella were dominant.

Acknowledgments

This paper is a modified version of my Master of Sciencethesis (Kaim 1995)prepared at the Institute of Geology of the University of Warsaw. I am deeply indebted to Professors Jerzy Dzik and Jeny Trammer for their support on all stagesof my work. I would also like to thank D. Bottjer, H. Hagdorn, M. Kowalewski, W. Oschmann,M. Machalski, K. Malkowski, and A. Piserafor reviews and helpful discussions. The photographs were taken by Ctru|yna and Marian Dziewiriski. Special thanks to 'strzelce Tomasz Hajdo (Cement Factory Opolskie') for help during my stay in Stzelce Opolskie.

References

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Zespoty ramienionogowo-m al2owe ze 6rodkowotriasowych warstw terebratulowych Dolne$o SQska

ANDRZEJ KAIM

Streszczenie W Srodkowotriasowych warstwach terebratulowych i w dolnej czg6ci warstw karchowic- kich w kamieniolomie w Strzelcach Opolskich wyr62niono pigi typ6w zespol6w ramienionogowo-malZowych: (1) zesp6lmuszlowc6w ramienionogowych, zdominowany ptzez Coenothyris vulgaris; (2) zesp6l wapieni gruzlowych i falistych, zawierai4cy malle i ramienionogi; (3) zesp6lmuszlowc6w mal2owych, zdominowany przez pseudokorbulidy; (4) zesp6l twardego dna, w kt6rym najliczniejszy jest ramienion6g Tetractinella trigonella; i (5) zesp6l wapienia hrynoidowego, zlo1ony ze szcz4tk6w liliowc6w i skorupek ramienionogaPunctospirellafragilis.Wystgpowanie wymienionych zespol6w skamienia- lo5ci w badanym profilu jest skorelowane z eustatycznie kontrolowanymi zmianami litologicznymi w wgglanowej sekwencji wapienia muszlowego na G6rnym Sl4sku. Musz- lowce ramienionogowe s4 parautochtonicznymi pozostaloSciami lawic terebratulowych, kt6re obficie wystgpowaty w warunkach wysokiej bioproduktywnoSci i niskiej zawartoSci tlenu. Takie warunki byly prawdopodobnie spowodowane przez naplyw skladnik6w od- Zywczych z obszar6w zalanych podczas transgresji Srodkowego triasu. Faza regresywna spowodowala stopniowe zmniejszanie produktywnoSci biologicznej i polepszanie warun- k6w tlenowych. I-awice terebratulowe zostaly zastApione przezlawice pseudokorbulowe. W trakcie postgpuj4cej regresji pojawily sig zespoly wskazuj4ce na dobrze natlenione Srodowiskaoligotroficzne (zesp6l twardego dna i zesp6l wapienia krynoidowego).Zaob- serwowane zmiany faunistyczneodzwierciedlal4t6Lnice w metaboliZmie i sposobieod|y- wiania dominuj4cych gatunk6w.