ZOBODAT - www.zobodat.at Zoologisch-Botanische Datenbank/Zoological-Botanical Database Digitale Literatur/Digital Literature Zeitschrift/Journal: Abhandlungen der Geologischen Bundesanstalt in Wien Jahr/Year: 1980 Band/Volume: 34 Autor(en)/Author(s): Matura Alois, Summesberger Herbert Artikel/Article: Geology of the Eastern Alps (An Excursion Guide) 103-170 ©Geol. Bundesanstalt, Wien; download unter www.geologie.ac.at Abh. Geol. B.-A. 34 p. 103—170 52 figs., 10 tables 26" C. G. I. Wien 1. 5. 1980 International Geological Congress 26tl) Session Excursion 034 A Geology of the Eastern Alps (An Excursion Guide) - by ALOIS MATURA and HERBERT SUMMESBERGER with contributions from ALOIS FENNINGER, WOLFGANG FRISCH, VOLKER HOCK, HEINZ KOLLMANN, ARTHUR KRÖLL, OTTO MALZER, JULIAN PISTOTNIK, BENNO PLÖCHINGER, ALFRED RÖGL, REINHARD ROETZEL, WOLFGANG SCHNABEL, HANS PETER SCHÖNLAUB and GODFRID WESSELY. 52 figures and 10 tables Address of the authors: Dr. ALOIS MATURA, Geologische Bundesanstalt, A-1031 Wien, Rasumofskygasse 23; Dr. HERBERT SUMMESBERGER, Naturhistorisches Museum Wien, A-1014 Wien, Burgring 7. ©Geol. Bundesanstalt, Wien; download unter www.geologie.ac.at 4 03 N RSIO Z> H p uX w t < LU ^ h LL LL h- Q ~ r r t O U 3 ve ou LU XC < H ir LU U U \ • D RO ©Geol. Bundesanstalt, Wien; download unter www.geologie.ac.at Acknowledgments drillings we know that the Molasse sediments continue The authors express their gratitude to F. FLIRI, D. VAN far below the Eastern Alps towards south. The crystal­ HUSEN, G. NIEDERMAYR, R. OBERHAUSER, A. RÖGL and line complex of the Bohemian Massif with a thin Palaeo­ A. TOLLMANN for their constructive comments. Many thanks zoic and Mesozoic cover forms the basement of the Mo­ are due to the Gebr. Leube Portlandzementwerk Gartenau, lasse Zone. the Quarzwerk Zelking, the Tonwerk Fritzens and the Vor­ The Helvetic Zone in Vorarlberg comprises Upper arlberger Zementwerke Lorüns for their generous permission Jurassic to Upper Eocene rocks. The primary neigh­ to enter their open pits. We are especially grateful to the prio- bourhood to the autochthonous Mesozoic is indicated rate of the Abbey of Kremsmünster, the österreichische by facial analogies. Small thickness, gaps, greensands Mineralölverwaltung AG and the Rohöl-Aufsuchungs GmbH because of their valuable support for our work. and reefs in the northerly region, and the abundance of marls in the southerly region indicate depositional conditions at the shelf edge. Day 1 The Penninic Zone in Vorarlberg is mainly represen­ ted by Cretaceous to Lower Eocene Flysch sediments. In Molasse Zone, Helvetic Zone, Flyschzone, Northern Cal­ general these synorogenic successions are rather poor in careous Alps, regional pattern of Vorarlberg fossils and have in many places been affected by syn- Route: Bregenz — Gebhardsberg — Schwarzachtobel — sedimentary movements. They have been deposited in Dornbirn — Götzis — Feldkirch — Frastanz — Lorüns different subsidiary troughs. — Arlberg Pass — Landeck — Innsbruck The Alpine movements did not only cause the com­ plex internal structure of the Penninic Flyschzone; Introduction moreover, the northern front of the Flysch Nappe has been overthrust by the normally underlying Hel­ Vorarlberg is an appropriate area to introduce into vetic Nappe. At the surface we can distinguish therefore the geological structure of the Eastern Alps. The section a northern and a southern Flyschzone in Vorarlberg. of the Rhine valley south of Bregenz between the Boden- The boundary plane between the Helvetic Zone and the see and the Principality of Liechtenstein can be taken Penninic Zone is marked by a strongly deformed as the topographic boundary between the Western and Schuppenzone. the Eastern Alps. Moreover, east of this line also the The Falknis-Sulzfluh Nappe and the Arosa Schup­ Austro-Alpine Unit begins and extends eastwards for­ penzone which tectonically overlie the Flyschzone have ming major parts of the Eastern Alps. The main geo­ also been allocated to the Penninic unit. Concerning logical units of the Western Alps (Helvetic and Penninic their depositional facies the Upper Jurassic to Paleo- Zones) continue towards east as a relatively narrow cene successions are different from the Flysch deve­ zone along the northern boundary of the Eastern Alps. lopment and thought to come from a more southerly The existing geological structure is the result of the region. The strongly deformed rocks of the Arosa Alpine orogenesis, a complex multiphase event. In Vor­ Schuppenzone directly underlie the Austro-Alpine Unit arlberg the main Alpine tectonic activity took place and mark its plane of overthrusting which can be traced during the Palaeogene. As a consequence of regional from Südbünden (Switzerland) northwards as far as compression with southward subduction of the fore­ Vorarlberg along the western and further eastwards to land, areas of Mesozoic to Tertiary sedimentary series the Allgäu (Bavaria) along the northern edge of the of different facial nature, in some places with slices of Austro-Alpine Unit. Moreover, the Arosa Schuppen­ their basement, moved from their site of deposition in zone appears in several tectonic windows in the western­ such a manner, that they overrode the neighbouring most area of the Northern Calcareous Alps as well as units in the north. together with lower Penninic units in the window of The main units from the top to the bottom are ordered Gargellen which is situated in the area of the Silvretta as follows: crystalline complex. Austro-Alpine Unit (Northern Calcareous Alps and Silvretta crystalline complex) The Austro-Alpine Unit in Vorarlberg is chiefly re­ Penninic Zone (Flyschzone) presented by the Permomesozoic series of the Northern Helvetic Zone Calcareous Alps and by the Silvretta crystalline com­ Foreland (Molasse Zone) plex. The latter consists of paragneisses and micaschists This corresponds with the paleogeographic order from and minor proportions of amphibolites and Early south towards north. Palaeozoic orthogneisses. Mesozoics and crystalline com­ The Molasse Zone forms the foreland. It comprises a plex are linked together by the narrow Phyllitgneis- thick succession of upper Eocene to Miocene clastic Zone and a late Palaeozoic clastic succession which ex­ sediments composed of the debris of the rising Alps. The hibits stratigraphic contact in the south against the older portions of the Molasse sequence have been envol- Phyllitgneis-Zone and continues into the Mesozoic series ved by folding and thrusting (Subalpine Molasse) into in the north. The internal structure of the Northern the orogenic movements. From geophysical surveys and Calcareous Alps is mainly the result of early Alpine 105 ©Geol. Bundesanstalt, Wien; download unter www.geologie.ac.at ""V. • --*"'*"' • * * r-. * j***"*" . n . * ^"MJndau V * J?* '/*^ ' * n * * J><^' x. / * / " n * / " n ^^ ". N >f\ _* _ v^3 . * Pfänder / _^-^ • _*—•**^ - •_*•*• rt jl f j\Bre?^M \" >^ ' ^^f^ ' . * "^^^^' ' Hochgrat * ' . J^ - 47"30' vsSSffiTil \ /^7^"\ ^-^^' " ' ^ " . • ' « ' • " V^ So ( ' >^>—^\^ " ' . Hittisau r. "S^^ ^T / ^\*w»V> \ T-^S\* n - _ J . ^**^*^"^ -V"'^ I 0 5 10kr- » Lustenai fa ^ . \ n ^ ^^M ^^F :i: •.<•• t ^.\ ii' ~ & r .^^^m i ^- . ^^^^^^Sl ••P- 1 i 1 i i i i I n^^^l^tflM^^vhU 1 /\ ^^^fHocnalpeSekopf / DornßTr.'nTW. CT K-:, * ,7 1 /iiliTfi Be zau pliüi • 1 ^ •1 / yfTTT^-rrrffT i 1 TirrfHiTrn? ' r 1' 1 7 /'I 1 n X Hohenems fL ' \\ 1111 WPPffffll 111 1 I Hoher IfSn 1 jl 1 | II *| || / wflllll IHJi 111! °l 1/3 /^*l Ü/M IS I ah*3ÖIZI S [^•»flKugelDIIII HI ,'„ , || Kanisfliir IM llllim lllllii 1111 IJlljIli!JM=^^ 11 : 4 III > / 1 „ « \\\\wi \\\\^^JAM A • - Rankweil J ^^m/ ^^^y Damüls A Warlh \ 1 /M\\H WfMl \ M • MP \\\\\W^ * / _s~- ? 0 ^ ^^^pl FrastanzV / ui3 £_•**—^^& *' 4 Lech iß1 äjr Li c h ^N. Nenzing f /Y~\ R( te Vr'an d A / *\*^\ y Dr i\ Schwe stern / Bludenz «^> V a\l u z J 1 / J^M r .angen A r 1 b e r g i ^H . ..p\ Dal ias "T "i Pass + y^ A Lor Li ns / 71 1 " * +. — \y+ + y Btl i 1 I < + + ( + / ^S\ ^Schru —^ + + 1 3 + « ^1 ^ , / ^-v i .(-GaflunaKopf / Scesaplana Falk lis / * ^M •Mittag-)+ . , :! ;::::: i :J:. •j2>*'*' """"~ "^sj • H spitze L + /" | + \ "*" + ^w^^. •' Q E38 O9 r^i" r-zn- Fig. 1: Tectonic sketch-map of Vorarlberg (modified after M. RICHTER, 1978). 1 = Foreland Molasse; 2 = Subalpine Molasse; 3 = Helvetic Zone; 4 = Schuppenzone; 5—7 = Penninic Zone; 5 = Northern and southern Flysch Zone, Prätigau Flysch; 6 = Falknis-Sulzfluh Nappe; 7 = Arosa Schuppenzone; 8 + 9 = Austro-Alpine Unit; 8 = Crystalline basement (Altkristallin); 9 = Northern Calcareous Alps; 10 = Major thrust-plane; 11 = Excursion stop. 106 ©Geol. Bundesanstalt, Wien; download unter www.geologie.ac.at (Cretaceous) movements. Three major subsidiary nappes can be distinguished from the top to the bottom: the Inntal Nappe, the Lechtal Nappe and the Allgäu Nappe. In Vorarlberg the influence of a very low-grade Alpine metamorphism is restricted to the southerly regions mainly resulting in a retrograde metamorphism of parts of the Silvretta crystalline complex. The Pleistocene history is proved by a broad variety of glacial phenomena. The glaciation attained a thick­ ness of about 1000 m. The Rhine valley was a very prominent glacier bed. The Rhine glaciers extended as far as 40 km north of the Bodensee during the glacial maximum. Stop 1.1. Gebhardsberg Foreland Molasse Top. sheet 111 Dornbirn The locality Gebhardsberg (590 m above sealevel) lies about 190 m above the Bodensee. Beside the parking place the Eggenburgian sandstone-conglomerate-(Nagel- fluh)-sequence (fig. 3, tab. 1) is exposed with low-angle north-north-west dip. The sandstones are overlain by several meters of conglomerates with thick crossbedding. The pebbles consist of yellowish more or less quartzose limestones thought to be derived from Flysch rocks. At some places the conglomerate contains oyster shells. Regarding the tectonic position the locality is situated in the Foreland Molasse. Here at its southern end the Foreland Molasse was lifted by the northward push of the Alpine thrust sheets resulting in a northward slope of the beds.