Olga Piros, Gerhard W. Mandl & Harald Lobitzer*
Keywords: Dasycladaceae, Dachstein Limestone, Triassic(Norian), Zaimkalk, Mandling, Austria
Abstract
As already pointed out by Kieslinger [1964] and Tollmann [1976a], the Zaimkalk sensu Trauth [1925] cannot be considered as an individual formation, but at least in part represents lagoonal Dachstein Limestone locally dominated by dasycladaceans. The dasycladacean assemblage is clearly governed by Diplopora phanerospora Pia. Further important taxa are Gyroporella vesiculifera (Gümbel) Pia and Gyroporella sp. Rather scarce taxa are Griphoporella sp., Heteroporella zankli (On), Heteroporella sp. and ?Diplopora tubispora O n , while Salpingoporella humilis (Bystricky) and Salpingoporella sturi (Bystricky) are very rare. Also the foraminifera-assemblage is dominated by taxa characteristic for lagoonal Dachstein, respectively Upper Rhaetian Limestone, as e.g. Aulotortus sinuosus Weynschenk, Angulodiscus sp. and Variostomatidae.
Zusammenfassung
Wie schon Kieslinger[1964] und Tollmann [1976a] betonten, kann der Zaimkalk sensu Trauth [1925] nicht als eigenständiges Schichtglied aufgefaßt werden, sondern stellt — wohl zu einem erheblichen Teil — einen stellenweise Dasycladaceen-dominierten lagunären Dachsteinkalk dar. Die Dasycladaceen-Assoziation wird von Diplopora phanerospora Piaabsolut dominiert. Weitere wichtige Taxa sind Gyroporella vesiculifera (Gümbel) Piaund Gyroporella sp. Untergeordnet finden sich weiters Griphoporella sp., Heteroporella zankli (Ott), Heteroporella sp. and ?Diplopora tubispora Ott sowie sehr selten Salpingoporella humilis (Bystricky) und Salpingoporella sturi (Bystricky). Auch die Foraminiferen-Assoziation wird von typisch lagunären Dachsteinkalk- bzw. Oberrhätkalk-Taxa dominiert, wie z.B.
Aulotortus sinuosus Weynschenk, Angulodiscus sp. sowie Variostomatidae.
Összefoglalás
Mint arra már Kieslinger [1964] és Tollmann [1976a] is rámutatott, a Trauth [1925] értelmében vett “Zaimkalk”
nem tekinthető önálló formációnak, hanem az — legalábbis jórészt — lagúna-kifejlődésű dachsteini mészkő, amelyre a dasycladaceák helyi dominanciája jellemző. A dasycladacea-együttes abszolút uralkodó faja a Diplopora phanerospora Pia. Fontos fajok még a Gyroporella vesiculifera (Gümbel) Piaés egy Gyroporella sp. Alárendeltek: Griphoporella sp., Heteroporella zankli (Ott), Heteroporella sp. és ?Diplopora tubispora Ott. Igen ritkák: Salpingoporella humilis (Bystricky) és Salpingoporella sturi (Bystricky). A foraminifera-együttes uralkodó alakjai, pl. Aulotortus sinuosus Weynschenk, Angulodiscus sp. és Variostomatidae div. sp. szintén a lagúna-kifejlődésű dachsteini, illetve felső-rhaeti mészkőre jellemzőek.
Introduction The Mandling Unit represents a tectonically isolated, elongated wedge of typical sediments of the Northern Calcareous Alps, which border the southern
edge of the Tirolicum tectonic unit (fig. 1). The Unit stretches roughly from Wagrein/Radstadt in the West towards the area of Gröbming/Paß Stein in the East.
v---* A d dresses of Authors: OLGA PlROS, Geological Institute of Hungary, Stefánia út 14, H -1 4 4 2 B udapest, Hungary. GERHARD W . Ma n d l, Ha r a l d LOBITZER, Geological Survey of Austria, R asum ofskygasse 23, A -1031 V ienna, Austria.
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Fig. 1. Geology of the Mandling Unit, according to Hirschberg(1965) and Mandl & Matura(1995)
1 P le is to c e n e d e p o s its , 2 R a m s a u a n d G u te n s te in d o lo m ite , 3 G r a u w a c k e n z o n e , 4 D a c h s te in lim e s to n e , 5 R e iflin g F m ., 6 E n n s v a lle y fa u lt s y s te m , 7 “ C a r d ita o o lit e ” , 8 W e r fe n F m ., 9 D a s y c la d a c e a n s a m p le
Fig. 2. Triassic sedimentary sequence of the Mandling Unit according to Mandl(in Mandlet al. 1987). Asterix indicates stratigraphic position of dasycladacean flora 1 Shallow water limestones, 2 Dolomitized platform carbonates, 3 Pelagic carbonates, 4 +/- siliciclastic marine sediments
The generally heavily tectonized Triassic sedimentary sequence (fig. 2; Mandl1987) is dominated by Ladinian/
Carnian Ramsau respectively Wetterstein Dolomite. The tectonic position is discussed e.g. by Hirschberg(1965), Lein(1976) and Tollmann(1976b).
Based on lithological comparison and traces of fossils Glimbel (1890) was the first who considered the cliff-building limestone of the Northern slope of Zaimwald as Dachstein Limestone. Already Trauth (1925) quotes various fossils (Megalodus sp., Thecosmilia sp., ?Montli- valtia cf. norica Frech and Chemnitzia sp.) which “with highest probability” point to the Norian age of the Zaimkalk of the Mandling Unit. As pointed out by Trauth
1925, 181 f. the Dachstein Limestone of Zaimwald in the Mandling Unit shows abundant fissures and voids stained by red pigment. Therefore Trauth considered, that this
“special development” deserved an individual formation name, namely “Zaimkalk”. Practically all later authors (e.g. Kieslinger1964, 138, 146 f; Hirschberg1965, 52 f.) considered this formation name as absolutely irrelevant and as a consequence the term “Zaimkalk” found acceptance not even in local literature. Hirschberg
(1965), 53 states that the “Zaimkalk” is typical Dachstein Limestone of reef-facies and observed already the m/dm- bedding on Heimischarte, however, like all former authors without mentioning findings of dasycladaceans. Lein (in Tollmann 1976a, 212) considers the “Zaimkalk” of the Mandling Unit as Tisovec Limestone, which shows in addition at Stoderbrünnl neptunian dykes filled by Late Tuvalian red Hallstatt Limestone.
The dasycladacean assemblage described below, however, can be clearly assigned to Norian (Rhaetian?) Dachstein Limestone. The dasycladacean-rich samples were collected in 1980 (Lobitzer et al. 1982) at a small cliff of light-grey Dachstein Limestone on the trail close to Heimischarte in direction to Eibenberg. In the course of forestry road construction this small outcrop was blasted, however, and exposures likely can be found also along the new tourist trail No. 6 immediately east of Heimischarte in direction to Eibenberg. The limestone shows no reddish staining as typical for the “Zaimkalk” of Zaimwald. Calcite veins are abundant and the preservation of the microfacies is fair.
Microfacies and Dasycladacean Assemblage The irregularly dm/m-bedded or even massive
Dachstein Limestone of Heimischarte is dominated by grainstones and packstones (biopelsparites) with typical biota of lagoonal facies. Dasycladaceans, solenopora- ceans and codiaceans predominate; gastropods, pelecypods, crinoids and foraminifers occur in variable quantities. Peloids, intraclasts and oncoliths are also common constituents; micritization of grains is abundant.
In addition also biointramicritic limestones (pack- and wackestones) with abundant black pebbles and similar biota, however, with more reef-derived faunal elements (e.g. corals, sponge and hydrozoan fragments) can be found locally. This type can be considered as a special development of member A of the Lofer cycle sensu Fischer(1964).
Among the foraminifers (det. E. Kristan-Tollmann) Variostomatidae and Involutinidae (e.g. Aulotortus
sinuosus Weynschenk, Angulodiscus ssp.) represent the characteristic elements.
The dasycladacean assemblage is absolutely dominated by Diplopora phanerospora Pia, followed in abundance by Gyroporella vesiculifera (Gümbel) Piaand Gyroporella sp.. Griphoporella sp., Heteroporella zankli (Ott), Heteroporella sp., ?Diplopora tubispora Ott, Salpingoporella humilis (Bystricky) and Salpingoporella sturi (Bystricky) occur in minor quantities. In addition Thaumatoporella parvovesiculifera (Raineri), Cayeuxia alpina Flügel and solenoporaceans/codiaceans indet.
can be observed.
In the surroundings of Brandscharte also scarce intercalations of member B —true loferites— were traced.
Here also lagoonal Dachstein Limestone, locally with megalodont shells with + 20 cm diameter, is predominant.
Conclusions
The proof of the presence of lagoonal Upper Norian/Rhaetian Dachstein Limestone in the area between Heimischarte and Brandscharte (Unterer Zaimwald) is important from different points of view:
— As already argued by former authors (Gümbel 1890, that at least a major part of the Dachstein Limestone is of lagoonal facies. This implies that part of the Mandling Unit sequence represents sediments which must have been deposited on a
carbonate platform in a much more “northern”
position. Based on findings of megalodonts also Trauth(1925), p. 181 considers the “Zaimkalk” as a variation of lagoonal Dachstein Limestone of most probably Norian (l.c.p. 183) age. Due to the mainly massive character Hirschberg (1965), p. 53 in contrary considers the Dachstein Limestone of Zaimberge as reef development. The tectonic situation of Mandling Unit will be discussed in a separate paper by (G. W. Mandl).
— Comparable dasycladacean assemblages have been reported as well from the Dachstein Limestone of near reef lagoon of Loserstraße outcrops and from Upper Rhaetian reefs e.g. in Adnet (Piros in Lobitzeret al. 1994).
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Acknowledgements The authors are indebted to the directors of the
Geological Surveys of Austria and Hungary for supporting this study in the frame of bilateral cooperation. Mrs. Edith
Kristan-Tollmann determined the foraminifera mentioned. She died during the preparation of this paper, which is dedicated to her memory.
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1 2 3
PLATE 1
Fig. 1 G y ro p o re lla ve sicu life ra (Gümbel) Pia (left side), H e te ro p o re lla z a n k li (Ott) (right side up), Z 1. J. x10 Fig. 2 G rip h o p o re lla sp. (left side in the middle),
S a lp in g o p o re lla h um ilis (Bystricky) (left side down), Z 1. J. x 10 Fig. 3 Involutinidae, (left side),
? D ip lo p o ra tu bisp o ra (Ott) (right side) Z 1. D. x10
Fig. 4 S a lp in g o p o re lla hum ilis (Bystricky) (right side in the middle),
H e te ro p o re lla z a n k li(Ott) (right side up), Solenoporaceae, (left side), Z 1. D. x10 124
125