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Late Triassic and early Jurassic dikes and fissures in the Dachstein Limestone in the Northern Calcareous Alps harbor mass occurrences of the rhynchonellide brachiopods Sulcirostra juvavica and Halorella amphitoma. To test recent hypotheses about their paleoecology, we characterized these habitats using petrography, carbon stable isotopes, and trace element patterns, and found no evidence for hydrocarbon seepage or hydrothermal venting. Thus the brachiopods lived under normal-marine conditions, in darkness and absence of local photosynthetic primary production, hence relying on the supply of limited and presumably small-sized food washed into the dikes and fissures. Because Halorella and Sulcirostra occur in dikes and fissures since the beginning of their stratigraphic ranges, these rhynchonellides are not relics of formerly widely distributed taxa, but instead are two genera that rapidly adapted to these habitats. Both Halorella and Sulcirostra occur also in late Triassic and early Jurassic deep-water settings such as deep-marine sills and hydrocarbon seeps, indicating that close phylogenetic relationships between submarine cave faunas and deep-sea faunas, as seen today, existed also in the early Mesozoic, albeit among very different taxa. Another analogy to the modern cave fauna is the wide but disjunct geographic distribution of Sulcirostra and Halorella, both found throughout the Tethys and Panthalassa oceans. Our findings support the view that submarine cave habitats were continuously colonized by new taxa throughout Earth’s history. Financial support was provided by the Fonds zur Förderung der wissenschaftlichen Forschung (FWF) through grant M1779-N29 to Kiel and Peckmann

V sklopu diplomske naloge smo preučili rdeče zapolnitve megalodontidnih školjk iz norijsko-retijskega Dachsteinskega apnenca v dolini pod Peski v Krnskem pogorju v Julijskih Alpah. Praviloma se megalodontidne školjke pojavljajo v podplimskem faciesu in so zapolnjene oziroma neomorfno nadomeščene z belkastim kalcitnim cementom. V našem primeru se poleg klasičnih zapolnitev pojavljajo tudi takšne, kjer so megalodontide popolnoma ali vsaj deloma zapolnjene z rdečim ali zelenim, rahlo lapornatim apnencem. Najlepše so tovrstne zapolnitve, razgaljene na plastnici znotraj zgornjetriasnega Dachsteinskega apnenca v dolini pod Peski v Krnskem pogorju. Poleg zapolnitev megalodontidnih školjk smo preučili tudi bližnje neptunske dajke, ki so zapolnjeni z apnenčevo brečo, z rdečkastim in ponekod rumeno-zelenim apnenčastim vezivom. Na raziskovanem območju se pojavljata dve smeri neptunskih dajkov z nekoliko različnimi zapolnitvami. Hipoteza diplomske naloge je bila, da je rdečkast sediment v megalodontidah enak vezivu breč v neptunskih dajkih. Na lokaciji smo odvzeli vzorce megalodontidnih školjk z rdečimi apnenčastimi zapolnitvami in belim kalcitnim cementom ter vzorce iz poleg prisotnih neptunskih dajkov. Nato smo pripravili 43 zbruskov, ki smo jih fotografirali, skenirali ter preučili z optičnim polarizacijskim mikroskopom. Z optično mikroskopijo smo ugotovili štiri generacije zapolnitev školjk ter dokazali, da je vsaj del dajkov zapolnjen z zgornjekrednim apnencem. Starosti sedimenta v megalodontidah žal nismo mogli dokazati, saj v sedimentu ni bilo biostratigrafsko značilnih fosilov, vendar domnevamo, da je sediment iz obdobja jure, ko je ekstenzijska tektonika povzročila razpad in poglabljanje Julijske karbonatne platforme ter posledično formiranje neptunskih dajkov. Sediment, naj bi se iz območja dajkov potem lateralno izpiral v delno raztopljene lupinice školjk in polžev v matični kamnini. Za nadaljnje raziskave bi bilo priporočeno izvesti še katodoluminiscenčno raziskavo, s katero bi še natančneje ločili generacije cementov. The thesis studies the reddish infilling of megalodontid bivalves of the Norian-Rhaetian Dachstein Limestone in the valley below the Peski Mountain in the Krn Range of the Julian Alps. Megalodontid shells are usually found in subtidal facies and are filled or neomorphically replaced with white calcite cement. In our case, in addition to the classic fillings, there are also specimens completely or at least partially filled with red or green, slightly marly limestone. A layer inside the Dachstein Limestone in the valley below the Peski Mountain provides the best insight into these picturesque infillings. In addition to the filling of the megalodontid bivalves, we also examined the nearby neptunian dikes, which are filled with limestone breccia with reddish and sometimes yellow-green limestone matrix. There are two generations of neptunian dikes with different shivering and fillings in the explored area. The research hypothesis of the thesis was that the reddish sediment in the megalodontides, and of the matrix in the breccias of the neptunian dikes was the same. Samples of megalodontid bivalvia with red limestone fillings, white calcite cement, as well as samples from the neptunian dikes were collected. Fourty-three thin-sections were photographed, scanned and examined under a optical polarizing microscope. Using optical microscopy, four generations of fillings bivalves were defined, and it has been proven that at least some of the neptunian dikes were filled with Upper Cretaceous limestone. Unfortunately, we could not prove the age of the sediment in megalodontides, since there were no biostratigraphically characteristic fossils in the infill , but we assue it is a Jurassic sediment as in this period the extensional tectonics disintegrated and deepened the Julian carbonate platform, and consequently caused the formation of neptunian dikes. We assume that the matrix from dikes was laterally washed into the partially dissolved shells of bivalves and gastropods in the host rock. Further research should focus on carrying out a cathodoluminescence study to further define the cement generations.

A new problematic microfossil is described as Coptocampylodon?rhaeticus n.sp. from the Rhaetian Dachstein Limestone of the NorthernCalcareous Alps. The new species is composed of a long cylindricaland an irregular rounded body, both showing narrow axial cavity.It is similar to Coptocampylodon? elliotti RADOIČIĆ 1969 from theCenomanian of Montenegro, but lacks the longitudinal grooves inthe cylindrical part. In the Alpine Dachstein Limestone it has beendetected at several localities where it occurs as an abundant constituentof biosparitic limestones along with the benthic foraminiferaTriasina hantkeni MAJZON, Aulotortus sinuosus WEYNSCHENK,Duostominidae and dasycladales Griphoporella curvata (GÜMBEL)and Diplopora adnetensis FLÜGEL.

The Dachstein limestone from Krn is characterized by Lofer development. The section encompasses 30 cyclothems on average 3-4 metres thick. Intraand supratidal environment of deposition is evident by stromatolites, loferite and tem­ pestile breccias. They were all locally affected by early diagenetic dolomitization. Biomicritic limestone with several horizons of megalodont clams was deposited in shallow and restricted shelf. Basal members A of the Lofer cyclothem are devel­ oped only exceptionally. Solution cavities are fairly common, being infilled by sparry calcite and insoluble rich red limestone. The limestone was deposited on the Julian carbonate platform near its passage part to the southerly lying Slovenian basin. In this part reigned specific circum­ stances that resulted into formation of very numerous corrosion vugs; they are filled in their central parts by variegated marly clay. Interesting are frequent temdoi:10.5474/geologija.1996.006