Early Permian carbonate shelf margin deposits: the type section of the Trogkofel Formation (Artinskian/Kungurian), Carnic Alps, Austria/Italy

Abstract

Herein the type section of the Trogkofel Formation (Artinskian/Kungurian) in the Carnic Alps (Southern Alps) is described. The locus typicus is mount Trogkofel, where a succession up to ~500 m thick of reefal to peri-reefal limestones is exposed. In the pedestal of mount Trogkofel, a succession of shelf limestones (Zottachkopf Formation) is sharply overlain by the unbedded Trogkofel Formation. Farther north, at Zweikofel, the boundary between a package of shelf limestones (Zweikofel Formation), and the overlying, clino-bedded Trogkofel Formation is a disconformity. Deposition of the Trogkofel Formation started after a backstep from shelf deposition (Zottachkopf and Zweikofel Formations) to a carbonate shelf-margin setting with buildups. The backstep was associated with tectonism.The lower to middle part of the Trogkofel type section is characterized by patch buildups grown in a foreslope to uppermost slope setting. Main buildup facies includes Tubiphytes-bryozoan-algal-cement boundstones, botryoidal-fibrous cementstones with Archaeolithoporella, and phylloid-algal bafflestones. The buildups are intercalated with intervals up to 10-15 m thick of bioclastic limestones. The upper ~100 m of the type section consist primarily of bioclastic grainstones rich in fusulinid tests and fragments of calcareous green algae; the bioclastic grainstone intervals episodically aggraded at least to near sea-level. The upper part of the section may result from (i) a shoaling because of moderate progradation-aggradation of the platform, or because of eustatic or tectonic sea-level lowering, and/or (ii) changed patterns of offbank sediment dispersal. In the Trogkofel Formation, soft-sediment to brittle deformation features record syn-to early post-depositional tectonism. Within paleokarstic caverns, 'intra-seismites' are represented by discrete, stacked packages of internal sediments with convolute lamination and/or intrabrecciation.Deposition of the Trogkofel Formation was terminated by uplift and subaerial truncation. Karstic caverns filled with geopetallylaminated lime mudstones to wackestones (typically dolomitized), and with caymanitic layers, reach to the base of the formation. Syndepositional deformation, and the uplift that terminated deposition of the Trogkofel Formation, may be related to the 'Saalian tectonic phase' . The truncation surface that caps the Trogkofel Formation is onlapped by carbonate-lithic breccias (Tarvis Breccia) that, on mount Trogkofel, probably accumulated from hillslope colluvium. The entire Tarvis Breccia and the upper part of the Trogkofel Formation are replaced by epigenetic dolomite. Down-section, dolomitization is tied to fractures and adjacent host rock, and to paleokarstic cavities and their vicinity. Dolomitization tapers out towards the base of the formation. Late-stage fractures and dissolution pores are filled with saddle dolomite.In dieser Arbeit wird das Typus-Profil der Trogkofel-Formation (Artinskium/Kungurium) in den Karnischen Alpen (Südalpen) beschrieben. Am locus typicus, dem...

Yakhtashian (Artinskian–Early Kungurian) cyanobacteria and calcareous algae from the Carnic Alps (Austria/Italy)

“…Taxonomic descriptions and systematics fol-the nineteenth century, and continued between the two World Wars by Heritsch, Kahler and Selli, who established the basic stratigraphic scheme summarized in Heritsch (1943). After World War II, paleontological and biostratigraphical studies as well as mapping were intensified, resulting in geological maps of the Naßfeld-Pramollo area (Kahler and Prey, 1963;Selli, 1963;Schönlaub, 1987;Venturini, 1990b;, refined biostratigraphical subdivisions, especially those of the Late Carboniferous and Early Permian, based on fusulinids (Kahler, 1985(Kahler, , 1986, as well as microfacies and facies models describing depositional patterns of reef and non-reefal shelf sediments such as those of Flügel (1971aFlügel ( , 1981; Buggisch et al (1976); Buttersack and Boeckelmann (1984); Venturini, (1990aVenturini, ( , 1991; Massari and Venturini (1990); Massari et al (1991); Krainer (1991, 1992, 1995a, 2007); Flügel et al (1997); ; Samankassou (1998,1999,2002,2003); Krainer et al (2003b); Sanders and Krainer (2005); Krainer and Schaffhauser (2012); Schaffhauser (2013); Schaffhauser et al (2015). Most studies involved 1) fusulinids summarized in Kahler (1985Kahler ( , 1986; and completed in Forke (1995,2000,2002); ; Forke and Samankassou (2000); Kahler and Krainer (1993); Krainer and Davydov (1998); Davydov and Krainer (1999); and Davydov et al…”

“…Recently, Schaffhauser (2013) and Schaffhauser et al (2015) studied the Trogkofel Formation at the type section. There, the Trogkofel Formation is up to 500 m thick and composed of massive to indistinctly bedded limestone.…”

“…Syndepositional deformation, and the uplift that terminated deposition of the Trogkofel Formation, may be related to the "Saalian tectonic movements." The truncation surface that caps the Trogkofel Formation is onlapped by carbonatelithic breccias (Tarvis Breccia) (Schaffhauser et al, 2015). The nonmarine Tarvis Breccia is composed almost entirely of reworked Trogkofel limestone clasts, indicating that the upper part of the Trogkofel Formation was subaerially exposed and eroded.…”

“…For example, calcareous algae from the Trogkofel Formation were mostly described from samples which were not collected at the type locality or type section. A type section of the Trogkofel Formation was first defined and described by Schaffhauser (2013) and Schaffhauser et al (2015). The large number of samples (and thin sections) from the lower Permian succession, particularly from the type sections of the Zweikofel, Zottachkopf and Trogkofel formations, which were taken for microfacies and micropaleontological investigations (e.g., Krainer and Schaffhauser, 2012;Schaffhauser, 2013;Schaffhauser et al, 2015), allowed us to study the algal assemblages in much more detail.…”

“…Remarks. Within the Trogkofel Formation, crudely laminated bindstones composed of cyanobacteria, probably Girvanella and other micritic-walled tubes form stromatolites up to 10 cm thick, which may be termed skeletal stromatolites according to Riding (1991) (Schaffhauser, 2013;Schaffhauser et al, 2015). In reef cavities millimeter-sized laminated sediments occur, which are composed of peloidal grainstone laminae and cement crusts (Schaffhauser, 2013).…”