Lower Permian conodonts from the Karavanke Mts. (Slovenia)

The first conodont fauna (4 species) from the "Trogkofel Limestones" of the Karavanke Mts. (Dolžanova soteska) is described and correlated with the fusulinids (3 species) within the same sample. The occurrence of Streptognathodus cf. simplex, Streptognathodus cf. elongatus and Diplognathodus expansus? together with Dutkevitchia complicata indicates a higher age (Asselian) of these limestones than previously thought, because even the Upper Pseudoschwagerina Limestone (Sakmarian) of the Garnie Alps already yields a Sweetognathus fauna. To avoid misunderstanding in correlations the name "Dolžanova soteska limestone member" is introduced for the white, pale red to red limestone unit, described as "Ttogkofel Limestone" in previous literature.


Previous work
The classical locality of Permian beds and fossils in Dolžanova soteska ("Teufelsschlucht" in German) in the Karavanke Mts. is situated in the Tržiška Bistrica valley, about 3 km NE of the tov^^n of Tržič in NW Slovenia (Fig. 1). In it the v^^ell exposed profile occurs in the Upper Carboniferous clastic beds, light grey, pale red and red "Trogkofel" limestones, dark, bedded limestones, Tarvisio breccia, Groden clastics and Upper Permian dolomites and rauhwackes. Although almost a century passed since the first systematic geological studies of these beds, the correct stratigraphie attribution of the up to nov^r improperly named light grey, pale red and red "Trogkofel" limestone unit remained still unresolved.
Since Geyer (1895) described the stratigraphy of the Garnie Alps, it vi^as generally accepted that the limestones of the Trogkofel are Early Permian in age. At this time the Rattendorf Group (Lov^^er Pseudoschw^agerina Limestone, Grenzland Formation, Upper Pseudoschwagerina Limestone) didn't exist and he included in his definition of the Trogkofel Limestone also the underlying dark or red, bedded limestones (now Upper Pseudoschwagerina Limestone). The fossils (mostly brachiopods), on which the biostratigraphic correlations were based, mainly came from these bedded limestones below. Three years later Schellwien (1898 a) described a fauna from the limestones of the Dolžanova soteska, which he compared with the limestones of the Trogkofel area (sensu Geyer). Between the rich brachiopod fauna, which he later described in his monography (Schellwien, 1900), he also found three ammonoids Agathiceras aff. uralicum Karpinsky, Popanoceras (Stacheoceras) n. sp., Thalassoceras? microdiscus Gemmellaro. But unfortunately there is neither a description nor a picture of these ammonoids. The stratigraphie subdivision and regional extension of the larger part of the Permian beds in the Karavanke Mts. were elaborated during investigations for the new geological map by Buser and Cajhen in 1978. Buser (1974 established the position of the "Trogkofel" limestone in Dolžanova soteska below the dark bedded limestones with Sphaeroschwagerina. Interesting for stratigraphy is the work by Pečar (1987) who determined a new brachiopod species in the "Trogkofel" limestone and ascertained that the Upper Carboniferous quartz conglomerate is overlain by the "Trogkofel" limestone.
All mentioned researchers of Permian beds in Dolžanova soteska assigned the grey, pale red to red limestones to the Trogkofel Stage without hesitation, which in the type region of the Carnic Alps is of latest Sakmarian to Artinskian age. Buser (1974Buser ( , 1980 and Pečar (1987) established the position of this limestone between the quartz conglomerate and the overlying dark bedded limestones with Sphaeroschwagerina. However, they did not deduce from this fact the possibility that the "Trogkofel" Иmestones of the Dolžanova soteska do not correlate with the true Trogkofel limestones in age.

Geological setting of Dolžanova soteska
The Upper Carboniferous and Permian beds outcrop in Dolžanova soteska in a 10km long and 3km wide east-west trending belt (Fig. 1). In spite of the very com-pHcated structure of the Karavanke Mts. this belt of younger Paleozoic beds is of relatively simple tectonics. A major obstacle to observations is the dense cover of several metres of weathering residue and of limestone slope talus. However, in the Dolžanova soteska the considered beds are well exposed, as the gorge cut deep into the rock sequence.
The Upper Carboniferous beds dip southwest below the Permian beds, therefore in the gorge from south to north gradually older beds are exposed. The Upper Carboniferous marine molasse beds are developed as shales, quartz sandstones and conglomerates with several metres thick intercalations of black limestones.
In Dolžanova soteska the predominantly massive quartz conglomerate, consisting of pebbles of quarzite and subordinately lydite in the upper part, attains about 180m thickness. The conglomerate is overlain by a 30cm thick black calcarenitic limestone with numerous crinoid fragments. The contact between conglomerate and limestone is uneven, very wavy and the conglomerate is intensely weathered and limonitized along the contact with the limestone. Laterally a 30cm thick sheet of quartz sandstone appears between the conglomerates and limestones. In the basal part of the calcarenitic limestone also quartz pebbles occur (Fig. 2). The uneven and limonitized surface of the conglomerate most probably represents an erosion that occured during the uplift of the sea bottom as a result of the tectonic phase near the boundary between the Upper Carboniferous and Lower Permian (Buser, 1974(Buser, , 1980. lm of grey limestone hes above the calcarenitic limestone that interbeds with up to several cm thick sheets of dark marl and shale. Upwards aim thick bed of dark grey biomicritic limestone follows. This limestone has the same dip as the basal contact plane in the conglomerate (212/75). Above the biomicritic limestone 50 cm of black mudstone is interbedded w^ith micaceous siltstone. 230cm of grey micaceous siltstones follow, which are tectonically strongly deformed and folded. The siltstone is covered by a 180 cm thick package of dark grey mudstone and marl. In limestones within the mudstone very numerous crushed brachiopod valves occur. It is most probable that Pečar (1987) found the brachiopod Capillomesolosus heritschi in these beds, which is, however, more frequent in the red and pale red limestones of Dolžanova soteska.
The content of mudstones decreases in the grey limestone, which passes into light grey, pale red and red massive limestones that have been called up to now "Trogkofel" limestones. This limestone is the main subject of this investigation and is called Dolžanova soteska limestone further on. The horizon, in which the colour changes, is not more than 2m thick. Upwards greyish to pale red limestones follow, which pass into the characteristic red limestones. In the latter the rich fauna of brachiopods as well as crinoids and common fusulinids occur. Schellwien's (1900) brachiopods originated from an ancient quarry 150 m north of the upper bend of the road through Dolžanova soteska. The limestones form more than 100 m high cliffs on the eastern side of the road. The limestone continues westwards across the Tržiška Bistrica. The length of the outcropping belt of limestone that is on the average 95 m thick amounts to about 2.5km.
The Dolžanova soteska limestone is of intense red colour in its highest part. From this limestone the samples for conodonts were collected in the steep cliff several ten metres above the road and above the abandoned quarry. The stratigraphie position of the considered Dolžanova soteska limestone can be observed about 100 m above the road and the abandoned quarry, since the intermediate area is covered by limestone rubble. Here the meat red limestone is overlain by brownish and greyish platy crinoid limestone that passes upwards into cinnabar red crinoid limestone (Fig. 3). On the upper surface of the limestone beds thin coatings of red-violet silty mudstone occur. This limestone is about 4m thick. Upwards about 5 m of grey red thicker bedded limestones follow. The crinoid limestone is overlain by 5 m of limestone breccia that consists of 5 to 30 cm sized fragments of biomicritic and crinoid limestone with brownish grey calcareous-sihceous cement. Laterally, quartz conglomerate and sandstone of approximately 1.5 m thickness may occur above the breccia.
The breccia is overlain by 3 m of micritic dark grey limestone that is covered by a 10m thick package of black limestone in alternation with black shale. The rock outcrops at the upper road curve. Upwards an about 200m thick succession of grey, thick bedded limestones with abundant Sphaeroschwagerina follows. The type locality of Sphaeroschwagerina camiolica (Kahler & Kahler, 1937) is situated in this limestone at this upper bend of the road. The characteristic pyramids of the Dolžanova soteska, and also the part of the rocks through which the road tunnel was driven about a century ago, consist of these dark bedded limestones.
The Lower Permian succession is terminated by a clastic sequence of interbedded quartz sandstones, conglomerates and shaly mudstones. The Middle Permian Tarvisio breccia and the violet-red clastics of the Groden Formation were deposited above these clastics. Material: 18 specimen DSB 5,8,10,11,12,13,14,21,27,30,32,33. Description: -Carminiscaphat with a slender, lanceolate platform. Specimen have a inward-downward trending curvature of platform immediately posterior to the end of the carina. Free blade long with 8-10 denticles, the second and third are the largest. Carina short and fused, 1-2 separated nodes are sometimes developed posterior to carina.

Conodonts
-Platform is divided by a median groove and possesses transverse ridges, which may pass sometimes the median groove, especially in the posterior part. On the anterior part of parapets nodes or small costae are developed and separated from the carina or fixed blade by deep furrows. The parapet of the inner side is usually somewhat longer than the outer one. -Oral surface of carina, transverse ridges and accessory nodes with a honeycomb ultrastructure.
Streptognathodus cf. elongatus Gunnell, 1933 PI. 1, figs. 7-9 Material: 13 specimen DSB 3,4,6,15,16,20,23,25,26,31. Description: -Carminiscaphat with a lanceolate platform. Specimen have a inward-dovmward trending curvature of platform immediately posterior to the end of the carina. -Free blade long with 8-10 denticles, by which the second and third are the largest. -Carina short, fused, seldom a single node is developed posterior to the carina. -Platform is divided by a median groove and possesses transverse ridges, which may pass sometimes the median groove, especially in the posterior part. On the anterior part of parapets nodes or small costae are developed and separated from the carina or fixed blade by deep furrows. The parapet of the inner side is usually somewhat longer than the outer one. The inner side of platform has a slight indentation in the anterior part, where the nodes are developed. -1-4 accessory nodes are attached at the inner side of the platform margin.
Description: -Shells of small size, elongate-fusiform with a minute proloculus (25 цт), first whorl almost round, later increases markedly in length. 4-5 volutions in mature specimen. -Wall is thin, two-layered with a dark outer layer (tectum), and light inner layer (diaphanotheca?). -Septa are very thin and regularly fluted.
Occurrence: Common together with Dutkevitchia complicata and Boultonia willsi in the Dolžanova soteska limestone member.
S cheli wi en mentioned that they occur together with Quasifusulina tenuissima in grey to yellowish limestones.

Faunal affinity and stratigraphie correlations
The stratigraphie occurrence of the genus Dutkevitchia is not well defined at the moment. However, the similar Dutkevitchia dastarensis (Bensh, 1972) was found in the "Obere kalkarme Schichtgruppe" (Auernig-Group) of the Garnitzen Section by Kahler F. and Kahler G. (1982). Dutkevitchia expansa (Lee, 1927), which has conspicious axial fillings in the inner volutions, occurs in the Lower Pseudoschwagerina Limestone. Dutkevitchia complicata is described from a red limestone in the Trogkar Section (assigned to the Trogkofel limestone) by Forke (1995), where it occurs together with Robustoschwagerina sp. This form differs from herein described species in having a more elongate, subcylindrical shape in the outer volutions. The occurrences of the genus Dutkevitchia are well correlatable vdth the C/P boundary type sections in Southern Urals and especially the Darvaz region as well as with Chinese sections, where they are reported from Uppermost Carboniferous to Sakmarian deposits. Dutkevitchia complicata seems to be restricted to the Asselian and Sakmarian.
The absence of the genus Sphaeroschwagerina in the studied material, which is the index fossil of the Asselian seems to depend on facies. Kahler F. and Kahler G. (1941) described Sphaeroschwagerina citriformis from a loose chunk of the Dolžanova soteska limestone. The dark limestones above yield Sphaeroschwagerina camiolica (Kahler & Kahler, 1937). Closely similar species (cf. Rauzer-Chernoussova, 1960) were often assigned by Russian and also Japanese researchers to Sphaeroschwagerina pav lovi (Rauzer-Chernoussova, 1938), which is a widespread Asselian fusulinid. Sphaeroschwagerina camiolica is also common in the Grenzlandformation of the Garnie Alps.
The fusulinid genus Quasifusulina as well as the conodont Hindeodus minutus are long-ranging species (Carboniferous -Permian) and have therefore no stratigraphical value.
Diplognathodus expansus? (some with a single row of nodes on the carina) are found together with Sweetognathus in the Upper Pseudoschwagerina Limestone and Trogkofel limestone? (Forke, 1995 (Wang & Higgins, 1989;Wang, 1994) the genus Diplognathodus is reported from Gzhelian to Low^er Sakmarian deposits.
Because no universally accepted taxonomy exists for the Upper Carboniferous-Lower Permian Streptognathodus, it is difficult to give a precise correlation for this species. Therefore, independent on exact taxonomic assignation, the widest range of Streptognathodus elongatus and Streptognathodus simplex is from Upper Carboniferous (base of Gzhehan) to Lower Permian (Sakmarian) strata.

Microfacies
Several additional samples were thin sectioned for microfacies study. They indicate a wide variety of shallow subtidal to intertidal? platform carbonates.
The thin sections of the sample from where the conodonts and fusulinids were obtained, are bioclastic wackestones. The bioclasts are mostly echinoderm fragments, as well as common fusulinids, smaller foraminifera, bryozoans, brachiopods and ostracods (Fig. 4). Large, unbroken phylloid algal blades are present, but their internal parts are normally not preserved (Fig. 5). They appear as moulds, filled with sparry calcite or fine peloidal micritic sediment after dissolution, showing geopetal structures, which could be also seen in some shelter pores of brachiopods. The phylloid algae were encrusted by Tubiphytes or red algae {Claracrusta sp.). Sponges, gastropods and trilobites are rare. Conspicious is the strong bioturbation (agglutinated worm tubes) of the sediment.

Conclusions
Although a latest Carboniferous age could not be strictly excluded for the grey, pale red and red limestones, an Asselian to earliest Sakmarian age seems more likely, because Diplognathodus expansus? as well as Dutkevitchia complicata are reported only from Lower Permian deposits at the moment. If the contact to the overlying dark, bedded limestones is sedimentary indeed, the upper range is limited because of the occurrence of Sphaeroschwagerina camiolica (Asselian). Compared to the Carnic Alps these limestones are older than the Trogkofel limestones of the type locality and even as the Upper Pseudoschwagerina Limestone, which yields Sweetognathus inornatus and Sw. aff. whitei without any species of Streptognathodus.
Therefore the grey, pale red and red limestones from which the conodonts and fusulinids were obtained can not be called "Trogkofel" limestones no longer, but should be named after the Dolžanova soteska -the Dolžanova soteska limestone.