Cretaceous Ammonites from Upper Austria 59-79 © Biologiezentrum Linz/Austria; Download Unter
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ZOBODAT - www.zobodat.at Zoologisch-Botanische Datenbank/Zoological-Botanical Database Digitale Literatur/Digital Literature Zeitschrift/Journal: Denisia Jahr/Year: 2014 Band/Volume: 0032 Autor(en)/Author(s): Lukeneder Alexander Artikel/Article: Cretaceous ammonites from Upper Austria 59-79 © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at Cretaceous ammonites from Upper Austria A. LUKENEDER Abstract: Lower Cretaceous ammonite faunas from Upper Austria are presented. Lithological, sedimentological and palaeoeco- logical studies over the last decade of the Lower Cretaceous (Northern Calcareous Alps, Upper Austria) uncovered rich spectra of Valanginian-Barremian ammonites. Distinct ammonite faunas derive from limestones, marls and sandstones of well know tec- tonical nappes from Upper Austria (e.g. Ternberg Nappe, Reichraming Nappe, Staufen-Höllengebirgs Nappe, Langbath Unit). The main sections are, from north to south, the KB1-A Klausrieglerbach 1 section (Schrambach Formation), the KB1-B Klaus- rieglerbach 2 section (Schrambach Formation), the Hirner section (Schrambach Formation), the Eibeck Section (Rossfeld For- mation), the Hochkogel section (Rossfeld Formation), the Traunkirchen section (Tannheim Formation) and the Kolowratshöhe section (Rossfeld Formation). Thousands of ammonite specimens were collected, prepared and described. The ammonite assemblages clearly indicate a Mediter- ranean character with intermittent short pulses of Boreal immigrants. The composition of the ammonite assemblages is clearly linked to environmental changes during Lower Cretaceous stages. Sea level changes and variations in climate triggered the evo- lution of ammonite species. The palaeontological studies on the Lower Cretaceous ammonite material increased the knowledge on palaeoceanographic and palaeoenvironmental conditions at the time of formation of the Northern Calcareous Alps in Upper Austria. The intermittent palaeogeographic situation of the Northern Calcareous Alps during the Lower Cretaceous serves as a key for understanding the ammonite distribution in the Mediterranean Realm. Keywords: Ammonites, palaeontology, geology, Lower Cretaceous, Northern Calcareous Alps, Upper Austria Introduction turbiditic sandstone intercalations (VAŠÍČEK & FAUPL 1996). The Schrambach Formation occurs in both, the Lower Cretaceous pelagic sediments are well lower and the upper Bajuvaric units. Contrastingly the known to form a major element of the northernmost siliciclastic Rossfeld Formation is characteristic for the tectonic units of the Northern Calcareous Alps (e.g. higher Bajuvaric units to the south. The limestones and Ternberg-, Reichraming-, Frankenfels-, Lunz-, Staufen- marly limestones of the Schrambach Formation are typ- and Höllengebirgs nappes). As noted by numerous au- ical sediments of pelagic to hemiopalagic enviroments thors (VAŠÍČEK & MICHALÍK 1999; STAMPFLI & MOSAR based on the sedimentation of calcareous muds and 1999; SCOTESE 2001; WAGREICH et al. 2008), the area oozes in deeper waters of the Penninic Ocean at that investigated (Northern Calcareous Alps) was situated time. The source area for the Rossfeld Formation and at the eastern border of the Alpine-Carpathian Block the sandstone intercalations of the Schrambach Forma- during the Early Cretaceous. This was located between tion was situated to the south of the basin (FAUPL 1979; the Penninic Ocean in the North and the Vardar FAUPL & WAGREICH 1992; VAŠÍČEK & FAUPL 1996, Ocean (= Meliata Ocean) in the South-East. 1998; EGGER et al. 2011). The Rossfeld Formation is re- In the Northern Calcareous Alps, Valanginian to stricted to southern parts of the nappes. It is interpret- Barremian cephalopod-bearing deposits are mainly ed as a synorogenic succession deposited at the begin- recorded in two different facies, the Schrambach and ning of the compressional deformation within the Aus- the Rossfeld Formation (PILLER et al. 2004; WAGREICH troalpine unit (FAUPL 1979; DECKER et al. 1987). The et al. 2008). Additionally the Aptian-Albian palaeogeographical reconstruction of the investigated Tannheim Formation and the Albian Losenstein For- area through the Lower Cretaceous shows that the sed- mation in can occur in the lower Bajuvaric units imentation of these turbiditic sediments, in the inter- (PILLER et al. 2004). Lower Cretaceous sediments of the nal and eastern parts of the Northern Calcareous Alps Valanginian-Barremian Rossfeld Formation comprise (southern parts of the ‘Bajuvarikum’) is apparently con- Denisia 32, zugleich Kataloge des turbiditic marls and sandstones, whereas the Valangin- nected with an uplift of the southernmost parts. The oberösterreichischen ian-Aptian Schrambach Formation consist limestones thickness of Lower Cretaceous sediments occurring in Landesmuseums Neue Serie 157 (2014): and marly limestones, with in its lower parts frequent the northern tectonic units of the NCA decreases to- 59-79 © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at Fig. 1: Locality map of Austria showing the Lower Cretaceous out- crops (white circles) within the Northern Calcareous Alps (grey). 1. KB1-A Klausriegler- bach 1 section (Schram- bach Formation), 2. KB1-B Klausrieglerbach 2 section (Schrambach Formation), 3. Hirner section (Schrambach Formation), 4. Eibeck Section (Rossfeld For- mation), 5. Hochkogel section (Rossfeld For- mation), 6. Traun kir - chen section (Tannheim Formation), 7. Kolowratshöhe section (Rossfeld Formation). wards the north. Geodynamical processes occurring Within the Northern Calcareous Alps deep-water within the basins involved were reviewed by FAUPL & carbonate and marls predominate in the Lower Creta- WAGREICH (2000). The dominating sandstone deposits ceous. Synorogenic clastic successions and marl facies of within the Tyrolic Unit (e.g. Rossfeld Formation) be- the Lower Cretaceous comprises Maiolica-type lime- come less prominent within northern nappes (e.g. Baju- stones at their base grading into a shale-limestone cyclic varic units; PILLER et al. 2004). This reflects either be- facies. Resedimented clasts of shallow-water Urgonian- ginning subduction of the Penninic Ocean in the North type carbonates (SCHLAGINTWEIT 1991) give evidence or the obduction of oceanic crust of the former Vardar that small carbonate platforms were present in northern Ocean at the boundary Austroalpine/Southern Alps parts of the NCA during the Early Cretaceous, but were (SCHLAGINTWEIT 1991). The Eastern Alps originated later completely eroded. The deposits are interpreted as within the northwestern Tethys palaeogeographic belt pelagic sediments of the deep-water shelf to slope of the due to repeated convergence between the European and passive margin of the Austroalpine microplate. The on- the African plate and intervening microplates. A Juras- set of siliciclastic synorogenic strata marked the change sic-Cretaceous, ‘Eoalpine’ orogeny was followed by to a tectonically active margin due to compression at Meso- and Neoalpine deformational events (FAUPL & the Austroalpine-Penninic margin (WAGREICH 2003; WAGREICH 2000). WAGREICH et al. 2008). The Austro-Alpine units are a characteristic unit of The Kimmeridgian - Early Berrasian Oberalm For- the Eastern Alps. Based on palaeomagnetic data the mation represents a pelagic deep-water limestone with Austro-Alpine domain is considered to be a partly inde- grey, cherty, bedded micrites including carbonate tur- pendent microplate situated along the northern margin bidites of varying thicknesses. The microfauna is domi- of the Adriatic (Apulian) plate, and represents the nated by radiolarians, calpionellids and foraminifera northern tip of continental fragments of African affinity (WEIDICH 1990; REHÁKOVÁ et al. 1996; BOOROVÁ et al. during the Cretaceous (STAMPFLI & MOSAR 1999; 1999). Turbiditic Barmstein Limestone beds within the Oberalm Formation contain a diverse fauna of calcare- STAMPFLI & BOREL 2002). Eoalpine deformation strong- ly influenced Cretaceous sedimentation and the forma- ous algae and foraminifera indicating an early Berriasian tion of sedimentary basins within of the Austro-Alpine age. The Upper Jurassic to Berriasian carbonate plat- forms of the Plassen Formation (SCHLAGINTWEIT & EBLI domain (WAGREICH et al. 2008). Thus, a complex histo- ry of synorogenic basins with strongly varying geometries 1999; GAW L I C K et al. 2006) can be regarded as the and short-lived subsidence and uplift events character- source for the resedimented shallow-water material. izes the Austro-Alpine realm, especially during mid- and The Oberalm Formation grades into grey micritic Late Cretaceous times. The best documented Cretaceous limestones and limestone-marl rhythmites of the successions of the Austro-Alpine domain are preserved Schrambach Formation (VAŠÍČEK & FAUPL 1999; RASS- within the Northern Calcareous Alps (NCA, Fig. 1). ER et al. 2003; LUKENEDER 1997, 1998, 2000; Aptychus Cretaceous deformation resulted in thrusting and fault- limestone and Ammergau Formation p.p. of some au- ing within the NCA (WAGREICH et al. 2008). thors) during the Berriasian. Sandy turbidites are large- 60 © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at ly absent in the Schrambach Formation, and the amount of marl intercalations increases upwards. Con- sidering different tectonic units of the NCA both the base and especially the top of the Schrambach Forma- tion are diachronous. In more internal nappe complexes of the NCA (Tirolic units west and south of Salzburg; Reichraming and Lunz nappes