Nannofossil biostratigraphy of the Late Cretaceous Nierental Formation, Northern Calcareous Alps (Bavaria, Austria)

11 Pages·1993·4.5 MB·English

by  Michael Wagreich

67
Zitteliana
INNSBRUCK
Fig.1:SketchmapoftheNorthernCalcareousAlpsofAustriaandBavariatogetherwiththe3localitiesmentionedinthetext.
between major localities. This diachronism resulted in the in Krenmayr (in prep.) and Krenmayr et al. (in prep.). In
usageofthebroaderterm „Nierentalfacies" forredandgrey general,thefaciesoftheNierentalFm.isinterpretedasaseries
marls and marly limestones of the Upper Gosau Complex of marl-rich turbidites of various thicknesses, interstratified
aecordingtoHerm(1962a)andOberhauser(1963). withhemipelagitesofhighcarbonateContents,depositedina
ArecentdetailedsedimentologicalanalysisbyKrenmayr(in slopeenvironment.Depositionaldepthsoftheuppertolower
ppraelpe.o)geboagsreadphoincaealrlireercfoancsitersuaentailoynssisbwyorkFabuyplButett(a1l.98(11)9a8n7d) tbhaethhyeamlipaerleagiintteersp(ree.tge.dBfurtotm&thHeefrormam1i9n7i8f;erBaultatss1e98m1b)l.agesof
helped towards a betterdefinition and understandingofthe Thispaperdealswith the biostratigraphy oftheNierental
lithofacies of the „Nicrental Formation" as a formal Formation based on calcareous nannofossils, which are
lithostratigraphicsubunitoftheGosauGroupoftheNCA.In correlated with the existing zonations of planktonic fora-
aecordance with most of the previous authors (e. g. Herm minifera.Nannofossilinvestigationswereperformedonsmear
1962b)wesuggesttousethelithostratigraphictermNierental slides and slightly concentrated samples under the light
Fm. only for Sediments of the Late Cretaceous and Early microscope.ThreemajorlocalitiesoftheGosauGroupofthe
TertiaryfillingoftheGosaubasinsoftheNCA.Thelithofacial NCAwereinvestigated(flg.1):theLattengebirgearea;thetype
characteristics,suchasthesignificanceofredcolouredpelites areaoftheGosauGroup,theGosauValley;andtheGarnsarea
and distinetive pelitic intervals interpreted as hemipelagitcs northofHieflau/Styria.
betweenturbiditicsandstonesandmarls,aredescribedindetail
ACKNOWLEDGEMENTS
The authors acknowledge the financial support of the fromtheAustrianAcademyofScienceto M.Wagreichasa
Austrian Science Foundation, Project P7462 under the contribution to IGCP Project 262 (Tethyan Cretaceous
guidanceofProf.P.Faupl(UniversityofVienna),andagrant Correlations).WethankM.JarnikforimprovingtheEnglish.
SAMPLING STRATEGY IN
2.
TURBIDITE-HEMIPELAGITE COUPLETS
Deep-water turbidites interbedded with calcareous hemi- e.g.inthelowerpartoftheRoteWandsectionintheGosau
pelagites are a common feature of the Nierental Fm. ofthe Valley area (Krenmayr, in prep.). The carbonate content of
NCA(Butt1981).Thesediment-gravityflowdepositsofthe theseturbiditicpelites,generallyrangingbetween22and65%,
Nierental Fm. have a great facies variability, ranging from decreasesslightlyfromthebasetothetop,whichisamirrorof
coarse grained debris flow/grain flow deposits and classical the grain size grading and increasing clay content of the
turbidites with completeor incompleteBoumasequences to turbiditeTe-division.
silt-mud-turbidites.ThethicknessesofthepeliticBouma-Te- The hemipelagic intervals ofthe investigated sections have
divisionsalsoshowagreatvariabilityfrommarlstonesonlya highercarbonateContents (55 to 85%) than theTe-intervals,
fewcentimetersthinintheLattengebirgesection(Butt1981) resultinginasignificanthigherresistivityagainstweatheringof
orparts ofthe Gams-Kohlhuber section, to abnormal thick thehemipelagic marly limestones. Hemipelagicintervalshave
peliticintervalsofafewmetersaboverelativelythinturbidites, thicknessesof2cmtomorethan50cminthe Lattengebirge
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section,2tomorethan60cmintheGosausectionsand5to30 Erosion of type 2 may be ubiquitous within turbiditic
cmintheGarnssections.Lightgrev,brownishandredcolours deep-water sections resulting in imprecise dating of zonal
aretvpicalforthehemipelagites. boundariesandnannofossilevents,especiallythosewhichrely
Nannofossil sampling of sections with turbidites inter- on the last oecurrence of a marker species. Sometimes
bedded with carbonate-rich hemipelagites is faced with a reworking of slightly older assemblages is indicated by a
twofold dilemma. On the one hand sampling of turbiditic suddendecreaseinabundancesandtheexclusiveappearenceof
marls should be avoided because ofthe great probabilitv of brokenspeeimen(e.g.samples44and45oftheLattengebirge
erosion and mixing with reworked, older nannofossil section,comp.fig.2).Zonalboundarieswhichmaybestrongly
assemblages.Ontheotherhandthecarbonatecontentofthe influenced by reworking are especially concentrated in the
turbiditic marls is more suitable for the preservation ofthe Latest Campanian - Early Maastrichtian, where the last
nannofossilsthanthehemipelagiclayers-carbonatecontents oecurences ofmarkerspecies like Eiffellithm eximius, Rein-
ofabout40to50%supplythebestpreservationconditionsin hardtitesanthophorus,BroinsoriM (Aspidolhhus)parca group,
thestudied samples, limitingbothdissolution anddiagenetic Quadrum group, Tranolithus orionatus, and Reinbardtites
overgrowthsofnannofossils. levis define the lower boundaries of the nannofossil zones
Theeffectofreworkinginnannofossilsamplesofturbiditic CC22ctoCC25aintheStandardzonationofSissingh(1977)
marllayerscanbeclassifiedbroadlyaecordingtothescaleand andPerch-Nielsen(1979,1985).
ageoferodedSediments:(1)Erosionofsignificantolder(>1-2 Bearing in mind these effects of reworking within the
nannofossilzones),mainlylithifiedstratainthehinterlandof turbiditic marls, hemipelagic intervals of the Nierental Fm.
the turbidite basin, resulting in a mixing of nannofossils of were preferentially sampled. Effects ofreworking should be
differentages,and(2)subaquaeouserosionandincorporation minimized in these layers although the action of bottom
ofshelforslopepelitesbyindividualturbiditeflows,leadingto currents or dilute „tails" of turbidity currents during the
themixingofslightlyolder(< 1-2zone)nannofossilswithan deposition ofthese „hemipelagic" layers cannotbeexeluded
autochthonousassemblage. (BuTT 1981). However, the high carbonatecontents ofthese
Withinthestudiedsectionsofthe LateCretaceous,type 1 hemipelagitic intervals result in stronger diagenetic over-
reworkingisclearlyasecondaryphenomena,althoughexten- growths and recrystallizations. Therefore, samples of the
sivereworkingofLateCretaceousSediments is knownfrom hemipelagic intervals sometimes show a bad preservation
overlying Paleocene turbidites of the Garns basin (e. g. potential with delicate forms strongly recrystallized to the
Kollmann 1964;Lahodynsky 1988).Tvpicalnannofossilsof extentthattheycannotbeidentifiedsafelvanylonger.Onthe
thelowerpartoftheGosausequences(Coniacian-Santonian) other hand a double sampling test of turbidite-hemipelagite
are missing almost completely in assemblages of turbiditic coupletswithinsmallintervalsofthesectionsdidnotresultina
marlsoftheNierentalFm.ofthethreeinvestigatedsections, significant higher biostratigraphic resolution. Despite the
although erosionofthese Sediments hasbeen proven bythe preservationaleffectsreportedabove,thenannofossilassemb-
oecurrence ofsomeblocks ofolderSediments within debris lages ofturbiditic marls and hemipelagic intervalswerevery
flowsandslumpmassesinthelowerpartoftheNierentalFm. similar.
in the Garns basin (e. g. Kristan-Tollmann & Tollmann
1976).The scarcitv ofsignificant erosion ofolderSediments Another problem for sampling work arises if the
during the Campanian-Maastrichtian compared with Paleo- bioturbationofthehemipelagiclayersandtheuppermostpart
ceneSedimentsisprobablvnotonlyaconsequenceofthelocal oftheturbiditic marlstone packages is very strong.Thiscan
paleogeographic Situation offlooding and subsidence ofthe leadtonearlvcompletemixingofthedifferentsedimenttypes,
NCA(Faupl et al. 1987;Wagreich 1991), but may also be especiallyinthecaseofthinly beddedturbidite-hemipelagite
related to a global sea level highstand duringthis time(e. g. couplets.Differentialnannofossilsamplingofhemipelagicand
Haqetal.1987),resultinginworldwidegeneraldecreaseofthe turbiditiclaversisnearlvimpossibleundersuchcircumstances,
erosional gradient and trapping ofthe eroded Sediments on ashappenedforexampleinpartsoftheGarnsareasections.
wideshelfareas.
NANNOFOSSIL B IO STRATI GRA PHY
3.
Ingeneralthepreservationofthenannofossilassemblagesis Burnettetal.(1992).Thislowlatitudenannofossilzonationof
bad, although the diversities are rather high; nannofossil theLateCretaceous iscorrelatedwiththeStandardplankton
abundances were sometimes higher in hemipelagic layers foraminiferalzonationoftheTethyanrealm(e.g.Butt 1981;
becauseofrelativelylessadmixtureofsiltandclayfragments Marks1984;Robaszynskietal. 1984;Caron1985).
comparedwiththeturbiditicmarls.Thenannofossilzonations
csacnhembeefcoormtphaerLeadtewCirtehtacteheousStoafndSairssdinngahnn(o1f9o7s7s)ialndzoPneartciho-n 3.1 LATTENGEBIRGE SECTION
Nielsen(1979,1985),withsomemodificationsatthesubzone The Lattengebirge composite section (Herm 1962; Butt
levelfortheSantonian-CampanianboundaryintervalbyWag- 1981;Hagn 1981;Risch 1988)includestheDalsenalmsection
REICH (1988, 1992) and for the Campanian-Maastrichtian attheeasternbankoftheRötheibach,theTaucherholzstuben-
boundary interval by Schönfeld & Burnett (1991) and weesection,andtheWasserfallgrabensection.Duetofaulting
v
inthelowerpartoftheWasserfallgraben,aconsiderablepartof Tertiaryboundarysectionwithnannofossilandforaminiferal
the Late Campanian part of the section may be strongly zonationswasdescribedbyHermetal.(1981).
reduced in thicknessoreven missing.Thebiostratigraphyof WithintheLattengebirgecompositesection31sampleswere
the Cretaceous part of the Lattengebirge was dealt with in examinedfortheirnannofossilcontent(fig.2).Somesamples
detailbyHerm(1962a,b,1981),Butt(1981),andRisch(1988), were also checked for planktonic foraminifera, especially
basedonplanktonicforaminifera. around the Santonian-Campanian and Campanian-Maas-
ThesectionStartsattheDalsenalmlocalitywithSantonian trichtianboundary.
shelfmarls,aecordingtotheforaminiferalfaunasreportedby The section ofthe Dalsenalm Starts with grey shelfmarls
Butt(1981)andowninvestigations.Thepartlycoveredsection incorporating sandstone tempestites of the Lower Gosau
oftheTaucherholzstubenweg[elevata zone, Butt 1981)and Complex(Faupletal., 1987)lyingslightlydiscordantlyover
theWasserfallgraben(calcaratatomayaorensiszone)makeup sandy limestones of probably Early Santonian age. A
theupperpartofthecompositesectionandshowthetypical SantonianageoftheshelfSedimentsisprovenbythepresence
lithology of the Nierental Fm. described above. In the ofnannofossilsindicativeofthenannofossilzonesCC16and
CO
uppermostpartoftheWasserfallgrabenadetailedCretaceous- 7a,togetherwiththeplanktonicforaminiferaDicarinella
asymetrica and Sigalia decoratissima (Butt 1981).The lower described by Herm et al. (1981). Due to the rather long
boundaryoftheCampaniancanberecognizedwiththehelpof sampling interval, the topmost nannofossil zones of the
the first occurrence (FO) of the planktonic foraminifera Maastrichtian(CC26a,b)werenotfoundduringourstudy.
Globotruncanita elevata, still associated with Dicarinella
alsiymmeesttroinecsa.,AisnignratyhemsaercltisonaboofuGtos3a5um(Waabgorveeicthhe19i8n8d,ur1a9t9e2d) 3.2 GOSAU SECTIONS
the FO of G. elevata is recognized within the nannofossil Published nannofossil investigations in the Gosau areaare
CO
subzone 7b, afew meters above the first occurrence of concentratedontheLowerGosauComplexup totheEarly
curved morphotypes of Luaanorbabdus cayeuxii. The foll- Campanian (Wagreich 1988, 1992) and the Cretaceous-
owingCampanianpartofthesection(Taueherholzstubenweg, Tertiaryboundary interval intheElendgrabenSWRussbach
baseofWasserfallgraben)isstronglycoveredanddisturbedby (Preisingeretal.1986;Lahodynsky1988).Kupper(1956)and
faulting.Nodetailedinvestigationsweremadewithinthatpart, Wille-Janoscheck (1966) indicated a Campanian to Maast-
althoughzonesCC19toCC20havebeenfound.Thetopofthe richtianagefortheNierentalFm.intheGosauareabymeans
Campanianistakenatthelevelofthelastoccurrence(LO)of of planktonic foraminifera. Two sections were chosen for
the planktonic foraminifera Globotruncanita calcarata (e. g. nannofossil sampling: the Elendgraben section southwest of
Marks1984;Robaszynskyetal. 1984).Thiseventfallswithin Rußbach(Wule-Janoschek1966;Lahodynsky1988)andthe
nannofossil Zone CC22. Above this, a succession of nanno- RoteWandsection1.5kmEoftheZwieselalm(Küpper1956).
fossilzonesCC22ctoCC23awasrecognizedupto60mbelow DetailednannofossilsamplinginthelowerpartoftheElend-
the top ofthe Maastrichtian. Here, the top of zone CC25a graben section resulted in the recognition of several major
followsimmediatelyabovezoneCC23a-zoneCC24ismis- faults. Therefore, only the Upper part of the Elendgraben
sing completely, probably due to normal faults running (starting1140mabovesealevel)belowtheK/T-boundarysite
oblique to thesampled section. Abovethefaults thesection could be used for biostratigraphic zonation and is reported
continues up to the Cretaceous/Tertiary boundary as itwas here. The most complete section of the Campanian elevata
GOSAU
= oI1-2
5E EE E
iv| turbidite-dom. interval gray hemipelagites
E] turb.-hemipel. mixed red hemipelagites
olistostrom gray shelf marls
common/rare • very rare/questionable * reworked
Fig.3:DistributionofnannofossilmarkerspeciesintheNierentalFm.oftheElend-
grabensectionoftheGosauValley.Explanationsseefig.2.
GOSAU
RoteWandSeclic
Fig.4:DistributionofnannofossilmarkerspeciesintheRoteWandsectionWofthe
GosauValley.Explanationsseefig.2;lithologyandSymbolsSeefig.3.
zonetothe"middle"Maastrichtianissituatedinthegorgeof ofthenearby Elendgrabensection,Startsintheupperpartof
the RoteWand,where Küpper(1956) has already found the CC22ab.Thetopofthisdistinctlithologicalunit,regardedasa
Late Campanian calcarata zone. The section up to the K/T lithostratigraphicmarkerhorizonwithintheNierentalFm.,is
boundaryintheRoteWandgorgedescribedbyLahodynsky alreadydocumentedinzoneCC23aintheRoteWandsection,
(19S8)wasnotsampledduetofaulting. 2nannozonesbelowthetopoftheredinterval intheElend-
TheElendgrabensection(fig.3)Startsabout170mbelowthe graben section. This points to the existence of highly
K/T-boundary within zone CC22c?, indicative of the diachronous(about 1-2Ma)lithofaciesboundarieswithinthe
Campanian-Maastrichtian boundary interval and the Early NierentalFm.oftheGosauarea.
Maastrichtian (Schönfeld & Burnett 1991). However,
Etffellitbuseximius,whoseLOdefinesthebaseofCC22b,is 3.3 GAMS SECTIONS
still present in thesesamples, rangingwell abovethe LO of IntheGarnsareathesecondCretaceous-Tertiaryboundary
Remhardütesanthophorus.ThisanomalousdistributionofE. site was found within the Gosau localities of Austria
emxaiymibueswdauseotnolyreowbosrekrivnegd.wAitdhiisntitnhcet,Elaebnodugtr4a0bemnstehcitciko,nraendd- (stLuadhyodayrensskiytua1t9e8d8)i.nTthheewseescttioonfsthienveKs/tTigastietde idnurnionrgthtehrins
colouredinterval,dominatedbyhemipelagicSedimentation,is tributariesoftheGamsbach:theSchweinbachsection(gorgeE
9pr5emsenbtelforwomthteheK/tTopboofunCdCar2y3.btothebaseofCC25a,about Tofoflalrmmainngnho&useTo"lSlommmaenrnau1e9r7"6,of1K99o1l),lmaanndnt1h9e64K,oKhrlihsutbaenr-
TheRoteWandsection(Fig.4)beginswithgraymarlsofthe section (gorge and western tributariesWeast offarming house
EarlytoMid-CampanianzoneCC20andwassampledupto "Kohlhuber" of Kollmann (1964); of farming house
230mabovethebase,whichisEarlvMaastrichtianaccording "Sattelbauer").The Schweinbach tributary provides a conti-
to markers indicative of the nannofossil zone CC23b. G. nuous, although partly covered section within basal
calcaratahasbeenfound 145mabovethebase,whichcorres- hemipelagitesandfollowingthinturbiditesinterbeddedwith
ponds to the nannofossil zone CC22ab. A red hemipelagic hemipelagites of the Campanian elevata zone to the Late
interval,about50mthick,verysimilartotheredhemipelagites Maastrichtian mayaorensis zone of the planktonic fora-
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1
anomalousrängeofthisspecieswithaLOwellabovetheLO AdetailedcorrelationwithinthelatestCampaniantoEarly
ofReinhardtitesantbophoruscanbeprovcn intheElendgra- MaastrichtiansubzonesofCC22 isalsohinderedbythefact
bensection.IntheLattengebirgesection,theexactpositionof thattheFOofReinhardtiteslevis,definingthebaseofCC22b,
theLOofG. calcaratacouldnotbeproven,probablydueto could not be precisely dated, due to overgrowth and
faultinginthispartofthesection.AccordingtoButt(1981), recrystallisation processes in carbonate-rich samples, which
G. calcarata has been found at the base of the rurbidite- makethedifferentiationofR. antbophorusandR. levisvery
dominatedpartofthesection,whichcanprobablvbecorre- difficult.Onlylarge(>10um)Reinhardtiteswithacompletely
latedwithnursamplesNo.Lg7or9h.SampleLg7(nannofossil closedcentralareaweregroupedintoR. ct. levis. As R. levis
zoneCC22b?)stillcontains a Late Campanian foraminiferal evolvesoutofR.antbophorusbyanincreaseinthesizeofthe
assemblagewithGlobotruncanitasubspinosa,whereasLg9his elementswhichsubsequentlvclosethecentralarea(e.g.Prins
alreadycharacterizedbyanEarlyMaastnchtianassemblageof &SissinghinSissingh 1977),thisdefinitionisquitearbitrary
Rugoglobigerinas without G. subspinosa and nannofossils andtheFOofR. levisisnotusedasareliablemarkerevent
indicativeofzoneCC22c. during this study. That is why the subzones CC22a and
CC22baregroupedtogether.
Plate1 NannofossilmarkerspeciesoftheCampanian-MaastrichtianottheGosauGroup
Allfigureswithcrossednicols,exceptFig. 1withS0Ccrossednicols
Fig.1 M.irtl\istcntesfurcatus(Detlwdri,inDEFLANDRE&Fert1954)DEFLANDRE,1939.ProbeLI8,Lattengebirge.
Fig.2 LucianorhabdusmaleformisReinhardt,1966.ProbeLIS,Lattengebirge.
Fig.3 Lithastrmusct.grilliiStradner,1962.ProbeEG35h,Elendgraben,Gosau.
Fig.4 LucianorhabduscayetixiiDEFLANDRE,1959.ProbeL1S,Lattengebirge.
Fig.5 Calculitesobscurus(Deflandre,1959)Prins&SiSSiNGH,1977.ProbeGAM131(calcaratahorizon),"Kohlhuber"section,Garns.
Fig.6 LucianorhabduscayeuxiiDeflandre,1959(ssp.BofWagreich1988).ProbeL18,Lattengebirge.
Fig.7 Broinsonia(Aspidolithus)ef.parcaparca(Stradner,1963)Bl'krv,1969.ProbeEG35h,Elendgraben,Gosau.
Fig.8 Broinsonia(Aspidolithus)parcaconstnetaHattner,Wind&WlSE,1980.ProbeGAM131(calcaratahorizon),"Kohlhuber"section,
Garns.
Fig.9 Broinsonia(Aspidolithus)parcaconstrietaHattnir.Wind&Wisi,19S0.ProbeEG90h(calcaratahorizon).RoteWandsection,Gosau.
Fig.10 Rucinolithussp.ProbeEGlS6h,RoteWandsection,Gosau.
Fig.1 ArkbangelskiellacymbiformisViKSH1N\.1959(smallspeeimen).ProbeLG43h,Lattengebirge.
Fig.12 ArkbangelskiellacymbiformisViKSHINA,1959(largespeeimen).ProbeGA17,Sehweinbachsection,Garns.
Fig.13 Ceratolithoidesaculeus(Stradner,1961)PrinsScSissingh,inSissingh1977.ProbeEG35h,Elendgraben,Gosau.
Fig.14 QuadrumgartnenPrins&Perch-NiiiSIn,inManinitetal.1977.ProbeEG186h,RoteWandsection,Gosau.
Fig.15 TransitionalformbetweenQu.gartnenandQuadrumgothicum(DEFLANDRE,1959)Prins&Perch-Nielsen,inManiyitetal.1977.
ProbeEG77h,RoteWandsection,Gosau.
Fig.16 QuadrumsissinghiiPiRCH-Nnisin,1986.ProbeEG35h,Elendgraben,Gosau.
Fig.17 Quadrumtrifidum(STRADNER,inSTRADNER&Papp1961)PRINS&PERCH-NlElsin,inMANIVTTetal.1977.ProbeEG90h(calcarata
horizon).RoteWandsection,Gosau.
Fig.18 Eiffellithuseximius(Saner,1966)PiRCH-NlELSEN,1968.ProbeL6,Lattengebirge.
Fig.19 Reinhardtitesantbophorus(DEFLANDRE,1959)Perch-Niiimn, 1468.ProbeEG35h,Elendgraben,Gosau.
Fig.20 Reinhardtitesct.antbophorus(Deelandre,1959)Perch-Nielsen,1968.ProbeL18,Lattengebirge.
Fig.21 Tranolithusononatus(RiINHARDT,1966)Perch-Nielsen,1968.ProbeEGlS6h,RoteWandsection,Gosau.
Fig.22 ReinhardtiteslevisPrins&Sissingh,inSissingh1977.ProbeEG90h(calcaratahorizon),RoteWandsection,Gosau.
Fig.23 Miculad.praemurus(Blrr-i,1973)Stradner&Steinmetz,1984.ProbeLG43h,Lattengebirge.
Fig.24 MiculasivasticaSir\dnikScSiiINMETZ,1984.ProbeEG77h,RoteWandsection,Gosau.
Fig.25 LtthraphiditespraequadratusRoth,1978.ProbeEG42t,Elendgraben,Gosau.
Fig.26 LtthraphiditesquadratusBRAMLETTI&Martini.1964.ProbeGA17,Schweinbachsection,Garns.
Fig.2" Micularnurus(Martini,1961)Blkrv.1973.ProbeGA17.Schweinbachsection,Garns.
Fig.28 CeratolithoideskamptneriBRAMIini ScM\rtini.1964.ProbeEGlS2t,RoteWandsection,Gosau.
Fig.29 Transitionalformbetween.1/.murusandMiculaprmsiiPerch-Nielsen,1979.ProbeGA17,Schweinbachsection,Garns.
Fig.3C BrokenspeeimenofMiculaprmsiiPerch-Nielsen,1979.ProbeEGlS2t,RoteWandsection,Gosau.
Zittcliana,20,1993
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Wagreich,M.&KrenmayrH.-G.:NannofossilsofthcNierentalFormation Tafel 1
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