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$CH D a \^^ \ *^Graz J$ ZOBODAT - www.zobodat.at Zoologisch-Botanische Datenbank/Zoological-Botanical Database Digitale Literatur/Digital Literature Zeitschrift/Journal: Austrian Journal of Earth Sciences Jahr/Year: 1999 Band/Volume: 92 Autor(en)/Author(s): Schönlaub Hans-Peter, Histon Kathleen Artikel/Article: The Palaeozoic Evolution of the Southern Alps. 15-34 © Österreichische Geologische Gesellschaft/Austria; download unter www.geol-ges.at/ und www.biologiezentrum.at VIM. )-:-::r :.ol. IS!3 \ o:->a\.i.-\'j:i 92 •!!)•>)• 3-1 WJr=n. Ju 2000 The Palaeozoic Evolution of the Southern Alps HANS P SCHÖNLAUB and KATHLEEN HISTON1 13 Figures Abstract In this article the present knowledge about the classic Palaeozoic sequence of the Austrian part of the Southern Alps is summarized. The available faunal, floral and sedimentological data are derived from a continuous record of Middle to Upper Ordovician through Upper Permian fossiliferous strata exposed in both the Carnic Alps and its eastward continuation in the Karawanken Alps. These data supplemented by palaeomagnetic measurements suggest a constant movement from more temperate regions of some 50° southern latitude in the late Ordovician to the equatorial belt during the Permian. Introduction en Alps, the Variscan sequence is almost completely cov The Carnic Alps of Southern Austria and Northern Italy ered by rocks of Triassic age. Further in the east, however, represent one of the very few places in the world in which an Lower Palaeozoic rocks are excellently exposed in the See- almost continuous fossiliferous sequence of Palaeozoic berg area of the Eastern Karawanken Alps south of Klagen age has been preserved (Fig. 1). They extend in a W-E- furt, the capital of Carinthia. Differing from the Carnic Alps, direction for over 140 km from Sillian in Tyrol to Arnoldstein in this region the Lower Palaeozoic strata are distributed on in central Carinthia. Continuing into the Western Karawank either side of the Periadriatic Fault (Gailtal Fault) which sep- (SK D A Graywacke Zone ^^^^ C ^-Innsbruck • ^ Burgenland \^^ \ *^Graz J CH //T Carnic Alps Karawanken Alps Fig. 1 Main occurrences of fossiliferous Palaeozoic rocks in the Eastern and Southern Alps (A = Austria, CH = Switzerland, CZ = Czech Republic, D = Germany, H = Hungary, I = Italy, SK = Slovakia, SLO = Slovenia, PL = Periadriatic Fault, Nö = Carboniferous of Nötsch). Address of the authors 1 Geological Survey of Austria, Rasumofskygasse 23, A-1031 Wien. E-mail: [email protected], [email protected] © Österreichische Geologische Gesellschaft/Austria; download unter www.geol-ges.at/ und www.biologiezentrum.at 16 H. F? SCHÖNLAUB & K. HISTON O CO to Ladinian 500-700 m Schierndolomit Formation -30 m Muschelkalk Formation < Anisian cc 0-30 m Muschelkalk Conglomerate t- Scythian 180m Werfen Formation z Tatarian 170 m Bellerophon Formation < Kungurian-Kazanian Tarvis Breccia Artinskian Tlrfreßdorf Lmst- cc Sakmarian 400 m Trogkofel Limestone UJ 175 m Upper Pseudoschwagerina Formation" CL Asselian 125 m Grenzland Formation 160 m Lower Pseudoschwagerina Formation" c/3 Gzhelian 600-800 m Auernig Formation o Kasimovian Moscovian Bashkirian o Serpukhovian CO cc Visean < Tournaisian o Famennian Frasnian z Givetian < z Eifelian O > LU Emsian Q Pragian Lochkovian Pridoli < Ludlow cc => _j Wenlock CO Llandovery z Ashgill < Caradoc < > Ü P wphyro?d^ " Fleons Formation ^immelberg Sst. \ Uggwa Shale > Llandeilo o > 1000 m Val Visdende Formation Q CC o © Österreichische Geologische Gesellschaft/Austria; download unter www.geol-ges.at/ und www.biologiezentrum.at 7 arates the Southern and the Central or Northern Alps. These quartzites and greywackes. They are overlain by more than rocks have been subdivided into a northern and a southern 300 m thick acidic volcanites and volcaniclastic rocks domain, respectively. The latter extends beyond the state named the "Comelico Porphyroid" and "Fleons Formation" border to northern Slovenia. respectively (Fig. 3), and their lateral equivalents compris In both the Carnic and Karawanken Alps systematic re ing the Himmelberg Sandstone and the Uggwa Shale. Lo search started soon after the foundation of the Geological cally, the latter contain rich fossils such as bryozoans, trilo- Survey of Austria in the middle of the last century. Interest bites, hyoliths, gastropods and cystoids indicating a Cara- ingly, the equivalents of the Lower Palaeozoic were first docian age (HAVLICEK et al., 1987). According to DALLMEYER found in the Karawanken Alps and not in the more fossilifer- and NEUBAUER (1994), detrital muscovites from the sand ous Carnic Alps (SUESS, 1868, TIETZE, 1870). In this latter stones are characterized by apparent ages (40Ar/39Ar) of area the main emphasis was drawn on marine Upper Car c. 640 Ma and may thus be derived from a source area boniferous and Permian rocks. At the end of the 19th century affected by Late Precambrian (Cadomian) metamorphism. this initial phase was followed by the second mapping cam This basal clastic sequence is capped by an up to 20 m paign carried out mostly by G. GEYER from the Geological thick fossiliferous limestone horizon of early Ashgillian age. Survey of Austria and detailed studies by F. FRECH, During It displays two lithologies, namely the massive "Wolayer the first half of this century F. HERITSCH (1936) and his Limestone" composed of parautochthonous bioclasts from research group from Graz University revised the stratigra cystoids and bryozoans, which laterally grades into the phy on the Austrian side, while M. GORTANI from Bologna bedded wackestones of the "Uggwa Limestone" represent University and others worked on the Italian part of the ing a more basinal setting with reduced thickness. mountain range. One of the outstanding contributions of In the Carnic Alps the global glacially induced regression that time focusing on the Lower Palaeozoic was provided by during the late Ashgillian Hirnantian Stage is documented VON GAERTNER (1931). The detailed knowledge of Upper by marly intercalations and arenaceous bioclastic lime Carboniferous and Permian rocks resulted mainly from stones of the Plöcken Formation which presumably corre studies by F. KAHLER beginning in the early 1930s. Since that sponds to the graptolite zone of Gl. persculptus (SCHÖN time many students of geology have started to visit both LAUB, 1996). If so, it may have lasted during the early and regions. During this third campaign study of various micro- middle Hirnantian Stage for not more than 0.5 to 1 million fossil groups began and other techniques were also ap years. It resulted in channeling, erosion and local non-dep plied. This research culminated in the publication of de osition. In fact, the succeeding basal Silurian strata general tailed maps, a new stratigraphic framework and revisions of ly disconformably rest upon the Late Ordovician sequence. old and discoveries of new faunas and floras (see e.g., Initiation of the aforementioned rifting and subsequent SCHÖNLAUB, 1971, 1980, 1985, 1997; SCHÖNLAUB and movements from higher to lower latitudes may be marked KREUTZER, 1994). by mafic volcanism occurring at various places in the East ern Alps in pre-Llandeillian strata (for references see SCHÖNLAUB, 1992). In the Southern Alps such rocks have not yet been recognized. The Late Ordovician faunal affini Review of Stratigraphy ties, e.g. brachiopods, nautiloids, cystoids, ostracods, con- odonts and vertebrate remains indicate links with Bohemia, Figure 2 summarizes the stratigraphy and facies distribu Thuringia, Baltoscandia, Sardinia and the British Isles tion of the sedimentary sequences of the Carnic Alps. With (SCHÖNLAUB, 1992; FERRETTI and BARNES, 1997; FERRETTI, minor modifications this framework can also be applied to 1997; BAGNOLI et al., 1998; BOGOLEPOVA and SCHÖNLAUB, the Karawanken Alps (SCHÖNLAUB, 1980; MOSHAMMER, 1998). Moreover, the appearance of carbonate rocks in the 1989). Late Ordovician suggests a position within the broader car bonate belt for this time. However, also a temporary cold- Ordovician water influx from northern Gondwana may have existed, as can be concluded by certain elements of the Hirnantia fau The oldest megafossil-bearing strata of the Southern Alps na, e.g. the genus Clarkeia appearing in uppermost Ordovi indicate an early Late Ordovician age. In the western Carnic cian strata of the central Carnic Alps (JAEGER et al., 1975). Alps and in the Brixen Phyllite complex even older rocks Based on the available evidence from the Ordovician of the occur the age of which, however, is not precisely known. Southern Alps SCHÖNLAUB (1992) inferred a palaeolatitudi- Presumably, the oldest part of this sequence may be attrib nal position at roughly 50°S. Originally this conclusion was uted to the Cambrian or Early Ordovician. based solely on lithic and faunal data but subsequently was In the Austrian part of the Southern Alps the Ordovician confirmed by palaeomagnetic measurements (SCHÄTZ et succession comprises weakly metamorphosed fine and al,, 1997). coarse clastic rocks named the Val Visdende Group. This more than 1000 m thick sequence is well exposed in the westernmost part of the Carnic Alps on both sides of the Silurian Austrian-Italian border. The lithology ranges from shales The Silurian strata of Austria are irregularly distributed and slates to laminated siltstones, sandstones, arkoses, within the Alpine nappe system with occurrences in the Gurktal nappe of Middle Carinthia and southern Styria, the <- Fig. 2 surroundings of Graz and the Graywacke Zone,

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