Search the Community

Dear Fossil Forum members! This report deals with ammonoids from the former zone of Protrachyceras archelaus, which is our present Longobardian within the Ladinian stage of the marine Triassic timescale. Fig.1 A beautiful view of the surging “rock waves” of the incoming tectonic thrust sheets. The valley between the two Mountains in the middle of the picture marks the tectonic border between the mainly Triassic Hallstatt Unit and the Tirolikum Unit of the Totengebirgs nappe (in the background). History Since the beginning of the geological research within the Northern Calcareous Alps of Austria in the middle of the 19th century, about 500 species of Triassic ammonoids have been described in great Monographs by Mojsisovics, Hauer, Diener and other early authors. The ammonoids described therein came from upper Anisian to uppermost Norian aged parts of the Hallstatt limestone in Austria. Only in the lower to middle Ladinian period, a gap exists in the rich ammonoid record of these early researchers. This gap was explained by them as an interruption of sedimentation in the Ladinian time or tectonically reduced Ladinian strata during the genesis of the Alps. During these early days no one thought of a collecting gap because Ladinian ammonoid faunae were well described and known from several localities in the Southern Alps and the Bakony Mountains in Hungary. In 1882 Mojsisovics pictured ammonoids of Anisian and Ladinian age in his monographic work “Die Cephalopoden der mediterranen Triasprovinz”. The locations mentioned therein reach from the upper Anisian Schreyeralm limestone here in Austria to several Ladinian locations of the former Austrian provinces Südtirol, Lombardy and the kingdom of Hungary, which were also part of the former Austrian-Hungarian Monarchy at this time. Included in this work were also Scythian and Anisian ammonoids from Croatia and Bosnia-Herzegovina. Fig.2 Frontpage of Mojsisovics second great monograph from the year 1882. “The detailed accurate descriptions and illustrations provided by Mojsisovics are unquestionably the greatest contribution by a single author towards appreciating the astonishing beauty and variety of Triassic ammonoids” (cit. E. T. TOZER). Therefore every recent Triassic ammonoid researcher includes these old works in the standard literature of Triassic ammonoids. These old works were so to speak, a cornerstone for building the marine middle and upper Triassic timescale of our days. Unfortunately the early stratigraphic scales of Mojsisovics had some mistakes. Originally the stratigraphic position of the “Norian” stage was set by him below the Carnian. He used the term Norian for the time frame we today call Ladinian. Mojs. thought that most parts of today’s real Norian Hallstatt limestone of Austria were of the same age as real Ladinian strata in the Southern Alps. Some misinterpret location data, i.e. the wrong assumed position of the fineclastic Zlambach marls as base of the Hallstatt limestone led him to this wrong assumption. It was the Austrian geologist Alexander Bittner, a contemporary of Mojsisovics, who introduced the term Ladinian into literature by recognizing the false assumptions of Mojsisovics. The name Ladinian was chosen by Bittner after the Ladinian folk of the Southern Alps/Dolomites. At this time this area was also part of the Austrian-Hungarian monarchy with its capital Vienna and it’s so called “Vienna school” of the palaeontology institutions there. Probably this “miss take” of Mojsisovics led to some changed ammonoid zones within the Norian timescale, which last into the 20th century. It was the merit of the Canadian Triassic worker E.T. Tozer to correct this long lasting error by establish his own North American Triassic timescale, based only on North American, mainly Canadian Triassic ammonoid locations. The pelagic (deeper marine) Triassic sedimentation in Austria starts with the uppermost Anisian Flexo-Ptychites beds/lenses of the Schreyeralm limestone. This is also the base of the Hallstatt formation. The next frequent ammonoid lenses/layers occur within uppermost Ladinian/lower Carnian strata in this formation. The lower to middle Ladinian time frame in between was not well documented with ammonoids by the early researchers of the 19th century. At some historical locations the lower Ladinian part is/was given but was not really recognised by them. Later, modern researchers used microfossils to determine the placement of large parts of the grey to violet limestone in the Hallstatt formation into the Ladinian. Within the 20th century also scarce ammonoids were mentioned from these middle Ladinian strata. Fig.3 Anisian Schreieralm limestone with cross sections of Flexoptychites sp. Fig.4 Monophyllites sphaerophyllus (HAUER) from the Schreieralm limestone In general, ammonoid locations are not frequently known within the Ladinian part of the Hallstatt limestone. The most common fossils are Crinoid stem parts, Bivalves and Conodonts. The limestone facies consists of red to grey, sometimes yellowish to grey coloured limestone which is locally interbedded with marls. Also strongly condensed successions are common there and fossils also do not occur in continuous layers. Comparable Ladinian ammonoid faunas are also well known from similar Hallstatt type limestone in Greece and Italy. They show similar ammonoid faunae of Ladinian to Carnian age. In the Tethys realm the whole Ladinium is split into two subdivisions today. Upper Ladinian = Longobardian, Lower Ladinian = Fassanian, The historical zone ammonite of the Longobardian is Protrachyceras archelaus (LAUBE). Fig.5 Protrachyceras archelaus (LAUBE), in MOJSISOVICS “Die Cephalopoden der mediterranen Triasprovinz“ Wien 1882 Tafel XXXL, Fig. 1, But Protrachyceras archelaus LAUBE do occur within a longer time span and is therefore not perfect for stratigraphic aims. The old archelaus zone of the Ladinian was therefore changed into several Longobardian and Fassanian ammonoid zones of today. Within the Tethys realm the Longobardian is split into the ammonoid zones of: Daxatina canadensis Frankites regoledanus Protrachyceras longobardicum The Fassanian is split to the ammonoid zones of: Eoprotrachyceras gredleri Protrachyceras margaritosum Eoprotrachyceras curionii The ammonoids shown in this report come from a condensed fossil bed roughly inserted to the turquoise marked ammonoid zones of the timescale below. Historical Ladinian locations The condensed lower Carnian fossil lenses on the famous historical Feuerkogel show almost all a portion of the upper Ladinian at their base. This is also visible at other Lower Carnian locations within the Hallstatt limestone. During the last years Proarcestes sp. from a new location are sometimes shown for sale in the internet. They are sometimes identified as Arcestes sp. from Norian strata. But it is Proarcestes, therefore its Norian age is definitely wrong. I visited this new locality a few years ago. All locations there are of Ladinian age which is evidenced by Proarcestes cf. subtridentinus, Anolcites sp. and Epigymnites sp. This fauna is maybe slightly younger than the fauna shown later here in this report. Fig.6 Some Epigymnites arthaberi (MOJS.) and Epigymnites moelleri (MOJS.) from the above mentioned location The new location Several years ago a friend and I were lucky to find a hitherto unknown middle Ladinian ammonoid location during a prospecting trip. At this location the normal limestone succession is penetrated by several fractures and tectonic influence across the normal layer direction is also visible there. The fossil layer itself, in which ammonoids were frequent, consists of a very strong condensed upper part of lower Longobardian age, indicated by Protrachyceras longobardicum (MOJS.), and a lower part of a slightly older age indicated by scarce last descendants of Ptychites cf. pauli MOJS. which show deeply incised second and third lateral saddles similar Aristoptychites or Arctoptychites. Therefore the location is ranged by me to the transition of the ammonoid zones of Protrachyceras longobardicum and the underlying Eoprotrachyceras gredleri zone. Outside of the Tethys realm this is roughly comparable to the zones of Meginoceras meginae MC LEARN and Tuchodiceras poseidon (TOZER) of the North American timescale. Both zones are known from the Triassic of British Columbia in Canada too. Tozer, 1994, wrote that flat forms of Protrachyceras sikianum MC LEARN are comparable with Protrachyceras longobardicum (MOJS.) and the thicker morphs of Pt. sikianum MC LEARN with Pt. archelaus (LAUBE). Fig.7 View of the lower, sometimes more greyish limestone part of the fossil layer. The chisel points to a Sturia cf. semiarata MOJS. The furrows on the limestone block have their origin in the strong condensation of this limestone. One can recognize by this feature the underlying part of a condensed limestone (fossil) layer. Fig.8 In contrast to the above shown picture, a view of the underside of the overlaying layer where craters/hollows are visible. These two features can be used for recognizing up and downside in strongly condensed limestone. This feature is independent from the Triassic age of the rock and occurs in condensed limestone of Jurassic age too. The right hanging limestone block contains the fossil layer. Fig.9 Protrachyceras longobardicum (MOJS). in situ. View from the underside. The upper half of the ammonoid was totally dissolved due to the extreme condensation of the uppermost limestone layer at this location. In this location P. archelaus occurs very scarcely. It is no good indicator for stratigraphic aims here at all. A normal collector can use the following features to insert ammonoids into the Ladinian timescale. The frequent occurrence of Proarcestes sp. with a wavy end body chamber is a sign for Ladinian age. All forms of Sturia sp. are restricted to the late Anisian and Ladinian. The occurrence of real Ladinian Protrachyceras MOJS. The following picture will show you the main differences between Protrachyceras, Trachyceras and Neoprotrachyceras. Fig.10 In contrast to Trachyceras the venter furrow of real Protrachyceras MOJS. is bordered by nodes which show a single point per node. Protrachyceras are restricted to the Ladinian. Real Trachyceras show “broader” nodes with two or three points a node bordering the venter furrow. Trachyceras is frequent in the Lower Carnian (Julian) The genus Neoprotrachyceras KRYSTYN looks similar toTrachyceras but shows also just one point per node, sometimes changing up to two points per node within maturity. Neoprotrachyceras is restricted to the uppermost Lower Carnian and lowermost Upper Carnian (e.g. the genus Spirogmoceras SILBERLING in the Dilleri Zone of the North American Tuvalian) For a newbie collector it is difficult to find some fossils in the Hallstatt limestone at all. To place them into the right ammonoid zone is sometimes the easier part of the exercise. Fig.11 A weathered cross section of Proarcestes sp., visible at the limestone wall. Notice the bleached limestone surface in contrast to the colour of the fresh rock. Fig.12 Talus block with visible cross sections of ammonoids and orthocone nautiloids Natural picture size is 20cm. The edges of the fossils are deeply weathered in. This can be a sign that the fossils will probably split out well. Small idiomorphic Biotite crystals up to one mm in size, fine Feldspar crystals and thin greenish tuffitic crusts around some ammonoids and limestone clasts indicate a distant simultaneous volcanic event, adjacent to the palaeo Hallstatt realm. This is the very first observation of volcanic fallout/washout within the Hallstatt limestone column. Within other tectonic nappes in the Northern and Southern Calcareous Alps (Dolomites) volcanic (Tuffitic) ash layers are a frequent feature in Ladinian time. In the adjacent Tirolic nappe some volcanic/tuffitic events are evidenced near the base of the archelaus zone. The middle Ladinian fauna listed below was found at this location. Ammonoidea cf. Beyrichites sp. Eupinacoceras cf. damesi (MOJSISOVICS). Epigymnites cf. ecki (MOJS.) Epigymnites cf. breunneri (HAUER) Epigymnites arthaberi (MOJS.) Gymnites raphaelis TOMMASI Megaphyllites obolus MOJS. Monophyllites wengensis (KLIPSTEIN) cf. Silenticeras sp. Sturia cf. sansovinii MOJS. Sturia semiarata MOJS. Proarcestes ombonii TOMMASI Proarcestes subtridentinus MOJS. Proarcestes .sp. Procladiscites sp. Protrachyceras archelaus (LAUBE) Protrachyceras longobardicum MOJS. Protrachyceras sp. Ptychites cf. pauli MOJS. Ptychites cf. plusiae RENZ Michelinoceras sp. Atractites sp. Syringoceras cf. longobardicus Nautilus div. sp. Bivalves Daonella sp. Peribositra sp. Brachiopoda: Discinisca sp. Austriellula dilatata (SUESS) Important ammonoid species of the archelaus zone A beautiful, conspicuous faunal element of the archelaus zone is Protrachyceras longobardicum MOJS. the zone ammonoid of the Langobardicum Zone This species shows its maximum roughly in the lower middle of the former archelaus zone and can be used well for stratigraphic aims. As mentioned earlier in this report compressed variants of Protrachyceras sikanianum MC LEARN are comparable to Pt. longobardicum MOJS. The thicker variants of Pt. sikanianum rather resemble Pt. archelaus LAUBE. Fig. 13 Protachyceras longobardicum MOJS. with Proarcestes ombonii TOMMASI and Proarcestes cf. subtridentinus MOJS. Fig. 14 Pt. cf. longobardicum, some juvenile Arcestes sp. and the brachiopod Austriellula dilatata. Fig. 15 Epigymnites breunneri (HAUER) and Monophyllites wengensis (KLIPSTEIN) Fig. 16 Epigymnites arthaberi MOJS. and Monophyllites wengensis (KLIPSTEIN) Fig. 17 Gymnites raphaelis TOMMASI Fig. 18Discinisca sp. Looks like a fossil Limpet gastropod (Patellidae) but in reality it is an inarticulate Brachiopoda Fig. 19Sturia cf. semiarata together with Proarcestes cf. ombonii The most frequent faunal element of the Ladinian within the Tethys realm is Proarcestes BRONN. This genus occurs with several species up to Carnian strata. In our location Proarcestes subtridentinus MOJS. and Proarcestes ombonii TOMMASI was often found. The second one can reach the dimension of a small ball. Fig. 20 Proarcestes subtridentinus Fig. 21 Monophyllites wengensis (KLIPSTEIN) In the Hallstatt limestone this genus starts with the Anisian Monophyllites sphaerophyllus via the Ladinian M. wengensis up to the Carnian M. simonyi. Within the descendants of the Triassic Phylloceratida the ancestor of the Jurassic Ammonitida is supposed. Fig. 22 Ptychites cf. pauli MOJS. This species of Ptychites show deeply incised second and third Lateral saddles. I think that this is a feature of allmost all "late" species of Ptychites. Fig. 23 Ptychites cf. plusiae RENZ Fig. 24 Sageceras walteri I hope you have enjoyed this new report about the Ladinian strata of my favourite collecting area. Again I thank, “Danke Roger”, Fossil forum member “Ludwigia” for correcting my “Austrian” English. Kind regards Andreas Literature: ALMA, F. H. (1926). Eine Fauna des Wettersteinkalkes bei Innsbruck. Annalen des Naturhistorischen Museums in Wien, 40, 111-129. BACHMANN, GH, JACOBSHAGEN, V (1974) Zur Fazies und Entstehung der Hallstätter Kalke von Epidauros (Anis bis Karn; Argolis, Griechenland). Z Deutsch Geol Ges, 125: 195-223 DIENER, C. 1900: Die triadische Cephalopoden-Fauna der Schiechlinghöhe bei Hallstatt. Beiträge zur Paläontologie Österreich-Ungarns und des Orient 13 v. HAUER, F. (1888). Die Cephalopoden des bosnischen Muschelkalkes von Han Bulog bei Sarajevo. KK Hof-und Staatsdruckerei. von Hauer, F. (1888. KK Hof-und Staatsdruckerei. KITTL, E., 1908, Beiträge zur Kenntnis der Triasbildungen der nordöstlichen Dobrudscha. Denkschriften der mathematisch-naturwissenschaftlichen Klasse der kaiserlichen: Akademie der Wissenschaften, v. 81, p. 445- 532 KRISTAN-TOLLMANN, E, KRYSTYN, L (1975) Die Mikrofauna der ladinisch-karnischen Hallstätter Kalke von Sakliblei (Taurus-Gebirge, Türkei). Sitzungsber. Österr. Akad. Wiss. Math. Naturwiss. Kl. Abt. I, 184 (8-10): 259-340 KRYSTYN, L. Zur Ammoniten und Conodonten-Stratigraphie der Hallstätter Obertrias(Salzkammergut, Österreich), Verh.Geol. B.-A., Wien 1973 KRYSTYN, L (1983) The Epidauros Section (Greece) – a contribution to the conodont standard zonation of the Ladinian and Lower Carnian of the Tethys Realm. Schriftenreihe Erdwiss. Komm. Österr. Akad. Wiss., 5: 231-258. MOJSISOVICS, E. 1893: Die Cephalopoden der Hallstätter Kalke, Abhandlungen der Kaiserlich-Königlichen Geologischen Reichsanstalt, II Band, Wien 1893 MOJSISOVICS, E. 1896: Beiträge zur Kenntniss der obertriadischen Cephalopoden Faunen des Himalaya, Denkschriften der Kaiserlichen Akademie der Wissenschaften Mathematisch–naturwissenschaftliche Classe, 63, 575–701. Wien 1896, TOZER, E. T. 1994. Canadian Triassic ammonoid faunas. Geological Survey of Canada Bulletin, 467, 1–663. MOJSISOVICS, E. V. 1879. Vorlaufige kurze Übersicht der Ammoniten-Gattungen der mediterranen und juvavischen Trias. Verhandlungen der kaiserlich- königlichen geologischen Reichsanstalt, 1879(7):133–143. MOJSISOVICS, E. V. 1882. Die Cephalopoden der mediterranen Triasprovinz. Abhandlungen der kaiserlich-königlischen geologischen Reichsanstalt, 10, 1–322. NITTEL, P. (2006) Geo Alp, Vol.3, S93-145, Beiträge zur Stratigraphie und Mikropaläontologie der Mitteltrias der Innsbrucker Nordkette(Nördliche Kalkalpen Austria) PISTOTNIK, U. 1973-74 Fazies und Tektonik der Hallstätter Zone von Bad Ischl — Bad Aussee (Salzkammergut, Österreich) RENZ, C. – 1931 Die Bulogkalke der Insel Hydra, Ostpeloponnes RENZ, C. (1910): Die mesozoischen Faunen Griechenlands I. Die triadischen Faunen der Argolis, Palaeontographica 58, S. 1-103, Tab. 1-7, Fig. 15 RENZ, C. Neue griechische Trias Ammoniten aus den Verhandlungen der Naturforschenden Ges. Basel. S. 218- 255, Tab. 6-8, Abb. l, Basel. SALOPEK M. 1911,Über die Cephalopoden der mittleren Trias von Süddalmatien und Montenegro, Abhandlungen der .k.k geol. Reichsanstalt, Band 16, Heft 3 WEITSCHAT, W. & LEHMANN, U. Stratigraphy and ammonoids from the Middle Triassic Botneheia Formation (Daonella Shales) of Spitsbergen With plates 1-6, 2 tables and 9 text-figures Mitt. Geol.-PaläonInst. Univ. Hamburg. Heft 54, S. 27-54 WENDT, J. (1970) Stratigraphische Kondensation in triadischen und jurassischen Cephalopodenkalken der Tethys. N. Jb. Geol. Paläont. Mh., 1970/7: 433-448