Foraminiferal Assemblages And Facies Associations In The Upper Jurassic Carbonates From Ardeu Unit (Metaliferi Mountains, Romania) Author Pleş, George Author Bucur, Ioan I. Author Păcurariu, Adriana text Acta Palaeontologica Romaniae 2015 2015-12-27 11 2 43 57 journal article 10.5281/zenodo.13190287 1842-371x 13190287 Labyrinthina mirabilis Weynschenk, 1951 ( Fig. 2 a-h) 1956 – Labyrinthina mirabilis – Weynschenk, p. 283, pl. 1, fig. 8. 1896 – Labyrinthina mirabilis – Mantea & Tomescu, pl 4, figs. 1-9. 1988 – Labyrinthina mirabilis – Septfontaine, p. 243, pl. 1, figs. 10, 12. 2005a – Labyrinthina mirabilis – Bucur & Săsăran, p. 30, pl. 2, figs. 3, 4. 2005 – Labyrinthina mirabilis – Schlagintweit et al., p. 31, fig. 13 a, b. 2008 – Labyrinthina mirabilis – Omaña & Gonzalez- Arreola, p. 803, fig. 7a. Fig. 1 Geological map of the BalȘa- Ardeu-Băcâia region (modified after Mantea & Tomescu, 1986 ) 1 Mesozoic ophiolites (CăpâlnaȘ- Techereu Nappe); 2 Oxfordian limestones (Ardeu Unit); 3 Kimmeridgian-Tithonian carbonates (Ardeu Unit); 4 Barremian-Aptian limestones (Ardeu Unit); 5 Aptian conglomerates and sandstones (CăpâlnaȘ- Techereu Nappe); 6 Albian breccia and sandstones (CăpâlnaȘ- Techereu Nappe); 7 Coniacian-Santonian siltites and sandstones; 8 Santonian- Campanian marls; 9 Santonian-Maastrichtian flysch deposits; 10 ?Maastrichtian-Paleogene continental deposits; 11 Badenian limestones; 12 Quaternary deposits; 13 Faults; 14 Nappe; 15 Location of the studied sections. Description: In early ontogenetic stage the test is planispirally coiled (up to 3 whorls), later becoming elongate, rectilinear up to 2.1 mm in lenght. The diameter of the coiled part ranges between 0.49 and 0.91 mm . Proloculus is globular. Chambers are separated by slightly convex septa. Vertical beams extend radially from the margins of the wall to the center, but not reaching it. Interseptal pillars are noticed in the adult uncoiled stage, mainly in the central part. They can be continuous from chamber to chamber (see Fig. 2c ). Wall agglutinated. Aperture is simple and interiomarginal in the enrolled stage, becoming multiple in the adult rectilinear stage. Remarks: In our samples, Labyrinthina mirabilis specimens are very abundant and identified in all ontogenetic stages. An important structural feature of this species is represented by the presence of the interseptal pillars. In early ontogenetic stages pillars are less evolved or absent, accounting for the simple morphology of the chambers and aperture. In the adult uncoiled part of the test, interseptal pillars are well formed and may develop a continuous trend throughout the chambers. The labyrinthic architecture of L. mirabilis can be the result of a random fusing process between beams and pillars in the adult stage. All of the L. mirabilis specimens are found free, in contrast to some encrusting forms illustrated by Weynschenk (1956) . The non-encrusting feature of the species was documented soon after by several authors ( Fourcade & Neumann, 1965 ; Gušić, 1968, Schlagintweit et al. 2005 ). Stratigraphic range: L. mirabilis is a widespread taxon in the Upper Jurassic carbonates of the Tethyan realm. It was first described by Weynschenk (1951) from the Upper Jurassic deposits of the Sonnwend Mountains ( Austria ). Other occurrences are listed in Table 1 . Loeblich & Tappan (1988) included the foraminifer Lituosepta recoarensis , described by Cati (1959) from Lower Jurassic limestones, into the synonymy list of L. mirabilis . Based on this fact, the authors extended the stratigraphic range of L. mirabilis from Lower to Upper Jurassic. Septfontaine (1988) in his evolutionary classification of Jurassic lituolids, clearly explains the main differences between the two taxa and restricts L. mirabilis to Upper Jurassic (as it was described) contrasting the Upper Sinemurian Lituosepta recoarensis . Bassoullet (1997) placed the stratigraphic position of this taxon between Uppermost Oxfordian and basal Tithonian.