ZOBODAT - www.zobodat.at Zoologisch-Botanische Datenbank/Zoological-Botanical Database Digitale Literatur/Digital Literature Zeitschrift/Journal: Beiträge zur Paläontologie Jahr/Year: 2005 Band/Volume: 29 Autor(en)/Author(s): Lukeneder Alexander Artikel/Article: An Early Cretaceous Ammonoid Association from Upper Austria (Late Valanginian, Northern Calcareous Alps) 1-13 ©Verein zur Förderung der Paläontologie am Institut für Paläontologie, Geozentrum Wien Beitr. Paläont., 29:1-13, Wien 2005 An Early Cretaceous Ammonoid Association from Upper Austria (Late Valanginian, Northern Calcareous Alps) by Alexander L ukeneder * ** Lukeneder , A., 2005. An Early Cretaceous Ammonoid Association from Upper Austria (Late Valanginian, Northern Calcareous Alps). — Beitr. Palaont., 29:1-13, Wien. Abstract Die Ammonoideen Fauna beinhaltet 7 verschiedene Gat­ tungen, von welchen jede durch mindestens 1-2 Arten Early Cretaceous ammonoids were collected at the repräsentiert wird. Das Vorkommen der Lokalität Hoch­ Hochkogel locality in the southernmost part of the Rei- kogel wird durch Bochianites (49 %), Ptychophylloceras chraming Nappe (Ebenforst Syncline, Northern Calcareous (18%) und Haploceras (18%) dominiert. Ancyloceratidae Alps). The cephalopod fauna sampled from marly parts of (durch Bochianites representiert) sind die häufigste Kom­ the Rossfeld Formation indicates Late Valanginian age. ponente. Ammonitidae und Phylloceratidae sind nahezu The ammonoid fauna comprises 7 different genera, each ausgeglichen (bei ca. 20 %). Lytoceratidae sind mit 7 % apparently represented by 1-2 species. The occurrence at unterdurchschnittlich vertreten. Ein einziger Tiefwasser the Hochkogel section is dominated by Bochianites (49 Nautilide und 2 Belemniten Rostren vervollständigen das %), Ptychophylloceras (18 %) and Haploceras (18 %). Bild der Cephalopoden Fauna. Brachiopoden, Muscheln Ancyloceratids (represented only by bochianitids) are the und Schnecken stellen die Hauptkomponenten der ben- most frequent component. Ammonitids and phylloceratids thischen Makro-Fauna dar. are roughly balanced (each about 20 %). Lytoceratids are In einem instabilen Umfeld kam es im Ober Valanginium represented with below average values (7 %). A single zur Ablagerung der Kalksteine, Mergel und Sandsteine deepwater nautiloid and 2 belemnite guards complete dieses Gebietes. Gravitativer Transport vom Herkunfts­ the cephalopod fauna. Brachiopods, bivalves and gas­ ort (im Süden gelegen) der verschiedenen Sedimente tropods make up the main components of the benthic und der fragmentierter Ammonoideen Exemplare wird macrofauna. angenommen. Die Cephalopoden Fauna zeigt einen rein The deposition of the limestones in this area occurred in Mediterranen Charakter. an unstable environment. Gravitational transport of dif­ Schlüsselwörter:Ammonoideen, Biostratigraphie, Unter- ferent sediments and fragmented cephalopod specimens Kreide (Valangin), Oberösterreich, Nördliche Kalkalpen is assumed for the accumulated layers from the source area (situated to the south). The cephalopod fauna consists solely of Mediterranean elements. 1. Introduction Keywords:Ammonoids, Biostratigraphy, Early Cretaceous (Valanginian), Upper Austria, Northern Calcareous Alps In the Reichraming Nappe (Bajuvaric Unit, Northern Cal­ careous Alps), Valanginian cephalopod-bearing deposits are recorded in two different facies, the Schrambach and Zusammenfassung the Rossfeld Formation. Upper Valanginian sediments of the Rossfeld Formation comprise turbiditic marls Unterkreide Ammonoideen wurden an der Fundstelle and sandstones, whereas the Schrambach Formation is Hochkogel im südlichsten Teil der Reichraming Decke built by limestones with turbiditic sandstone intercala­ (Ebenforst Mulde, Nördliche Kalkalpen) gesammelt. tions (V a i'cek & F aupl , 1996). The source area for the Die Cephalopoden Fauna aus den besammelten merge­ Rossfeld Formation and the sandstone intercalations of ligen Schichten der Rossfeld Formation, deutet auf Ober the Schrambach Formation was situated to the south of Valanginium hin. the basin (Faupl & W agreich , 1992; V asicek & Faupl 1996, 1998). The Rossfeld Formation is restricted to southern parts of *) Dr. Alexander L ukeneder , Department of Geology and the Reichraming Nappe. It is interpreted as a synorogenic Palaeontology, Natural History Muesum, Burgring 7, succession deposited at the beginning of the compressional A-1010 Wien, Austria, e-mail:alexander.lukeneder@ deformation within the Austroalpine unit (Faupl , 1979; nhm-wien.ac.at D ecker et al., 1987). The palaeogeographical reconstruc- ©Verein zur Förderung der Paläontologie am Institut für Paläontologie, Geozentrum Wien 2 Beitr. Paläont., 29, Wien, 2005 Gosau Rossteld Jurassic sediments 1 Upper Triassic f Frankenfels - Lunz Group Formation L..Al including Schrambach Formation fcËÎj Formations l Nappe System river fault forest road thrust 1 0 Km © sample location alpine pasture <8> mountains Figure 1: Fig. la. Locality map of Upper Austria showing tectonic situation (Reichraming Nappe, Frankenfels Nappe) around the section investigated within the Northern Calcareous Alps. Fig. lb. Position of the Hochkogel locality and lithological formations of the Ebenforst Syncline. tion of the investigated area through the Lower Cretaceous 2. Geographical setting shows that the sedimentation of the Rossfeld Formation (sandstone intercalations within the lower part of the The outcrop is situated in the Reichraming Nappe in Upper section), in the internal and eastern parts of the Northern Austria. The exact position is about 5 km south of Brun- Calcareous Alps (southern parts of the ‘Bajuvarikum’) is nbach (652 m, OK 1:50,000, sheet 69 GroBraming, Fig. apparently connected with an uplift of the southernmost 1). The outcrop is located in the southernmost part of the parts. This reflects either beginning subduction of the east-west striking Ebenforst Syncline along a forest road, Penninic Ocean in the North or the obduction of oce­ running between the Sulzkogel (840 m) to the north and anic crust of the former Vardar Ocean at the boundary the Hochkogel (1157 m) to the south at the topmost part Austroalpine/Southern Alps (S chlagintweit , 1991). The of the Reixengraben at 885 m. stratigraphy of the Lower Cretaceous sediments around The grey sandstone succession comprising the marly the investigated area is based on ammonoids. A new ammonoid-bearing beds (dipping 225/60°) is located on cephalopod fauna was collected in limestone interbeds of the nothern side of the Hochkogel, on a nearly vertical the Rossfeld Formation. wall of the outcrop, which was exposed by road-cutting. During the 1990s, a rich cephalopod fauna was collected The occurrence is exposed in 3 distinct beds of 10-40 cm from Lower Cretaceous sediments from the surrounding thickness (fig. 2). The exact position of the ammonoid-oc- area of the herein presented locality (V asi'cek & Faupl , currence is fixed by GPS data (global positioning system): 1996, 1998, 1999; V asi'cek et al., 1994; see also Immel, N 47°47’ 15” and E 14°30’00” (fig. 2). 1987). The present contribution provides a detailed study of the rich and extraordinarily well-preserved Upper Valangin- 3. Geological setting and lithology ian ammonoid fauna from the Hochkogel section, which yields new and important biostratigraphical data, and The Upper Valanginian cephalopods described here were presents new facts on the correlations within the Northern collected from a little outcrop containing sandstones and Calcareous Alps. The Hochkogel fauna is also correlated marly limestones, located at the southern margin of the with the comparable faunas from the most recent papers Ebenforst Syncline. The Ebenforst Syncline is situated in on Lower Cretaceous faunas of Lukeneder (1997, 1998, the southernmost part of the Reichraming Nappe of the 2001a, b, 2003, 2004), L ukeneder & H arzhauser (2003) Northern Calcareous Alps. This region is part of the Baju and V asi'cek & F aupl (1996, 1998, 1999). varic Unit, which is neighboured and overlain in the sou ©Verein zur Förderung der Paläontologie am Institut für Paläontologie, Geozentrum Wien Lukeneder , A., An Early Cretaceous Ammonoid Association... 3 c B -1 Marly limestone with sandstone intercalations flank of the Hochk eX*3ans'0n t*le ammonoid beds within the log of the investigated outcrop at the road-cut on the northern ©Verein zur Förderung der Paläontologie am Institut für Paläontologie, Geozentrum Wien 4 Beitr. Palaont., 29, Wien, 2005 by the Tyrolian Nappes (Staufen-Hollengebirgs Nappe). however, even extraordinarily well-preserved individu­ The Ebenforst Syncline is followed directly to the north by als (e.g. lappets of microconchs) could be collected. The three additional synclines - the Anzenbach Syncline, the casts show perfectly preserved sculpture on the preserved Schneeberg Syncline of the Reichraming Nappe and the shell. Losenstein Syncline of the Temberg Nappe - all of which In most cases the specimens are fragmented and show are constituted by Lower Cretaceous sediments. considerable tectonic deformation, which hampers precise The locality is situated 500 m north of the border to the determination to species level. The ammonoid fragments southern Tyrolian Units and is tectonically shifted into the show original body-shape preservation and are not flat­ Weyer Arc Structure. The Ebenforst Syncline is formed tened as is usually the case in Lower Cretaceous sediments of a Jurassic sequence (Oberalm Formation, Scheiblberg- in most Austrian localities. They are orientated