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 car- bonate-dominatedsequence of the Upper Silesian Muschelkalk. The brachiopod coqui- nas 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 transgres- sion. During the regressive phase, that resulted in the gradual decreasein bioproductivity and parallel increase in oxygen levels, the Grebratulid banks were replaced by pseudo- corbulid banks. With the further regression - and thus, the further increase in oxygen level - pseudocorbulid banks were replaced by the assemblagesindicative of well-oxyge- nated 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 s 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 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.