FEATURED AND RECENTLY ADDED FOSSILS

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late palaeozoic Sedimentary Evolution of the Southern Karavanks

 

Wavy-lenticular lamination and bedding in carbonate beds due to pressure-induced intrastratal dissolution. Early Permian, the central Southern karavanks.

Late Palaeozoic sedimentary evolution of the Southern Karavanks and Carnic Alps spanning the Middle Ordovician to Permo-Triassic boundary is marked by collisional uplift of the Variscan orogenic belt reaching its climax in the Moscovian. Pre-Variscan basement is unconformably overlain by post-Variscan sequence separated in two evolutionary cycles by a major intra-Permian tectonic event. Middle Ordovician to early Late Carboniferous sediments affected by Variscan orogeny are overlain by coastal to shallow marine silicilastic-carbonate sediments of the Late Carboniferous age. In the Early Permian commenced carbonate-dominated marine shelf sedimentation (Rattendorf and Trogkofel Groups) interrupted by a phase of uplift and erosion, which was followed by a new transgressive sequence with the red-beds of Groden Formation and the dolomites and evaporites of the Bellerophon Formation in the Late Permian.

Pre-Variscan Evolution (Middle/Late Ordovician to early Late Carboniferous) 

The Southern Karavanks represent orographic and morphological continuation of the Carnic Alps (Diener, 2002). The lithologic similaritiy and location south of the Periadriatic fault system implies a similar palaeolatitudinal setting of both regions

(Hubmann et al, 2014)  comprising two Palaeozoic sequences separated by a major uncoformitiy caused by the Variscan orogeny. The Prevariscan units of the Carnic Alps (Middle Ordovician – early Late Carboniferous)  and Southern Karavanks (Late Ordovician – early Late Carboniferous)  were depositing throughout the Ordovician on the peri-Gondwanan shelf in the southern realm of the Rheic Ocean  expanding at the expense of the Iapetus and Tornquist Oceans as the northern-Gondwana-derived microcontinents e.g. Avalonia drifted northwards toward Baltica and Laurentia. After the closure of the Tornquist Ocean by accretion of Avalonia to Baltica in the Late Ordovician and of the Iapetus Ocean by the collison of Laurentia and Baltica-Avalonia in the Silurian which lead to the formation of Laurussia, palaeogegraphic affinities of the present day alpine Carnic Alps and Southern Karavanks are more vague.

 

Two end-member models of the evolution of European Prevariscan units south of the former Avalonian margin of Laurussia, including those of the Alpine domain, have emerged. These units represent 1.) individual or composite terranes that rifted away from Gondwana, or 2.) remained attached to the northern Gondwanan margin throughout the Paleozoic.

 

1a: In one view of the first model,  a train of composite terranes, e.g. Armorican Terrane Assemblage and  Proto-Alps, rifted away from Gondwana by the Late Ordovician and  successevely accreted to the Avalonian margin of  Laurrusia at various times in the Palaeozoic, prior to the terminal collision between two major conitents in the Late Carboniferous (Tait et al., 2000, Schaetz, 2004). The drift was accompanied by gradual replacement of the endemic faunas of the departed terranes by those of Baltic and Avalonian affinities (Schonlaub & Histon, 1999; 2000).

 

Fig. 1: Early Ordovician to Late Carboniferous drift hystory of the Gondwana-derived continental fragments including Protoalps (highlighted in red) (after Schaetz, 2004).

 

1b: In another view, rather than a set of terranes a vast ribbon-like terrane-assemlage (superterrane) split-off Gondwana in the Siluro-Devonian and collided in the Late-Devonian-Carboniferous with the Laurussia-derived fragments and eventually Laurussia itself (Stampfli et al., 2002); von Raumer & Stampfli, 2008). 

 

In a now abandoned scenariol the Prevariscan sequece of the present day Carnic Alps and Southern Karavanks was deposited on the Palaeotethyan shelf at the trailing edge of the European section of Hun superterrane (Stampfli et al., 2002) (Fig.2) (the term is now reserved for another terrane detached coevally with Avalonia and subsequently accreted to the North China block) split-off from Gondwana in the Silurian. The supposed engine behind Hunic drift was Rheic slab-rollback while slab pull tiriggered back-arc spreading along Laurussian margin.

 

Fig. 2: Early Ordovician to Late Carboniferous drift hystory of the Gondwana derived continental fragments. Approximate position of the Carnic Alps and Southern Karavanks indicated by red dot (after Stampfli et al., 2002).

 

In the more recent model, dual polarity of subduction and slab-rollback on both sides of the Rheic ocean led to back-arc spreading along the opposing margins of the Ocean in the Devonian. Ribbon-like continents, termed Galatian Superterane and Hanseatic terrane, detached from northern Gondwana and Avalonian margin of Laurussia respectively. At the onset of rifting in the Middle Devonian the Galatian Superterrane  was flanked by the Rheic Ocean to the north and, folllowing its separation from Gondwana in the Late Devonian, defined the boundary between the passive-margined Palaeotehys and active–margined Rheic Ocean. Similarly, a narrow Rhynohercynian ocean opened with the separation of the Hanseatic terrane from the Avalaonian margin of Laurussia in the Late Devonian.  The Galatian Superterrane, not necessarily above the sealevel, soon fell-apart into several terranes by-passing each other. According to this view the Prevariscan sediments of the future Carnic Alps and Southern Karavanks were deposited on the Palaeotethyan shelf of the constituent Intra-Alpine terrane sensu stricto (= Proto-Alps). (Fig. 3a). The leading Gretaer Galatian terranes collided in the Late Devonian with the peri-Laurussian terranes, resulting in closure of the Rheic Ocean and subduction reversal. The Palaeotethys and Rhenohercynic oceans started to dive under the collage, creataing new subductions zones along its respective margins (Fig. 3b).  The ammalgamated terranes, uplifted into cordillera in the collison, eventually docked to Laurussia in the Early carboniferous (Fig. 3c). Therefore the Variscan orogenic event was a multi-stage process emanating from the collision between the terranes detached from Gondwana and Laurussia and subsequent collsison of the amalgamated terranes with Laurussia. The final collision of Gondwana with Laurussia (Fig. 3d) resulting in Alleghenian Orogeny did not occure before the Late Carboniferous. Afterwards the Variscan belt of Europe represented a transitional zone between the continental type of collsion to the west and the still active north Palaeotethyan margin to the east (Raumer & Stampfli, 2008; von Raumer et al., 2009; 2013, Stampfli et al. 2011; 2013).

 

Fig. 3: Late Devonian to Late Carboniferous drift hystory of the Galatian Superterrane, originally termed Greater Galatian Superterrane  (Stampfli et al., 2008). comprising four sub-terranes: Meguma, Armorica, Ibero-Ligerian and Intra-Alpine sensu lato. The scope and position of the Intra-Alpine terrane sensu stricto (= basement areas of the present-day Alps (Helvetic, Penninic, Austoalpine and Southalpine), Montagne Noire-Maures and Carpathians) highlighted in green (only 3a). The Intra-Alpine terrane sensu lato comprises Intra-Alpine s.str. + south- and eastward exposed basement units , e.g. Dinaridic, Sardinian, Hellenidic, Anatolic and Pontidic. Approximate position of the Carnic Alps and Southern Karavanks indicated by red dot (Slightly modified after Stamfgli et al., 2011; von Raumer et al., 2013).

 

2: According to the second model the present-day Variscan Europe, i.e. south of the Avalonian crust, (Greater Galatian od Hunic superterrane) remained integral part of the northern Gondwanan margin throughout the Palaeozoic until the collison of Gondwana with Laurussia in the Late Carboniferous, implying the Palaeotethys ocean never came into existence or existed only as a narrow ephimeral sea.

 

Either way, the closure of the Rheic Ocean in the Carboniferous culminated in its western domain in the Variscan orogeny (von Shonlaub & Histon, 1999; 2000; Tait et al., 2000; Schatz et al., 2002; Schatz, 2004; Raumer & Stampfli, 2008; Nance et al., 2012; von Raumer et al., 2013, Stampfli et al., 2002; 2011; 2013) accompained by light grade metamorphism and deformation of the Prevariscan sequence (Schonlaub & Forke, 2007; Forke et al., 2006; Brime et al., 2008, Corradini et al., 2015; 2017; Hubmnann et al., 2014).

 

The Prevariscan basement of the Carnic Alps and  Southern Karavanks is considered part of the external belt of the European Variscides (Mader & Neubauer, 2004), that was subsequently extensivelly deformed by the collisonal tectonics that gave rise to Alps (Fig. 4).

 

Fig. 4: Structural map of the European Variscan fold belt, excluding blocks of southeastern Europe e.g. the Hellenidic, Dinaridic and Pontidic.  After Schaetz, 2004.

 

According to Frisch & Neubauer (1989) the Prevariscan units of the Southern Karavanks were deposited on consolidated shelf of the Noric terrane = Noric Composite Terrane, comprising all pre-early Late Carboniferous fossililiferous sequences of the eastern Southern Alps (exposed in the Southern Karavanks and Carnic Alps) and Upper Australpine (exposed in the Greywacke Zone, Gurktal Nappe, Nötsch Carboniferous, Graz Palaeozoic and isolated outcrops in Southern Styria and Burgenland) (Neubauer & Handler, 1999; Schaetz, 2004; Tait et al., 2000; Mader & Neubauer, 2004). The Noric Terrane,  termed Noric-Bosnian Zone (Flugel, 1990),  Noric-Bosnian Terrane  (Nubauer & Raumer, 1993; Neubauer & Handler, 2000) when expanded to various Dinaric and Carpathian units with similar depositional history, represents one of the Proto-Alpine (Schaetz et al; 2002, Schaetz 2004)  or Intra-Alpine (Stampfli, 1996) terranes (not to be confused with Proto-Alps or Intra alpine terrane as a whole) forming Prevariscan basal units of the present day European Alps. The Noric sequences (fig. 4) record late Ordovician crustal thinning and rifting at the northern Gondwanan margin and deposition in a back-arc setting, followed by the Silurian to Devonian formation and Early Carboniferous destruction of passive continental margin as the Noric terrane collided (Neubauer & Handler, 2000; Neubauer et al., 1999) in the Early Carboniferous with other Proto-Alpine terranes successively accreted onto the southernh margin of Laurussia (by then including terranes accreted in the Silurian-Devonian e.g. Avalonia, Armorican asseblage) throughout the Devonian-Early Carboniferous (Tait et al., 2000). Proto- or Intra-Alpine terrane-assemblage was considered part of the vast ribbon-like composite Hunic terrane by Stampfli et al. (2002) or Greater Galatian Superterrane (von Raumer & Stampfli, 2008) described as having  collided with Laurussia and the peri-Laurussian Hanseatic terrane respectively. (von Raumer et al., 2002)  (Frisch & Neubauer, 1989; Neubauer & Handler, 2000; Neubauer et al., 1999, Stampfli, 1996;  Stampfli et. al., 2002; Schaetz, 2004; Tait et al., 2000; von Raumer et al., 2002; Stampfli et al., 2002; von Raumer & Stampfli, 2008). The composite basement of Noric terrane fomed by ammalgamtion of the preexisting Celtic and Speik terranes is covered by the Late ordovician – Early Carboniferous sequence deposited on a consolidated shelf showing continuous deepening (Frisch & Neubauer, 1989) further accelerated due to seafloor-spreading-related thermal subsidence at the mature passive margin and/or subduction of the plate approaching the subduction zone (see below) (Stampfli, 1996; von Raumer et al., 2013; Stampfli et al., 2013).

 

Faunal and lithological evidence speaks for the northern Gondwanan position of the Noric terrane throughout the Cambro-Ordovician and the paleomagnetic data point to subsequent continuous drifting of from 47° S  in the Silurian to equatorial belt in Permian, reflected in faunal-affinities and lithologic record (Schaetz, 2004). Following the rifting initiation in the Late ordovician, proven by bimodal volcanism in the western Carnic Alps (Hubich et al., 1999), the Prevariscan sedimentary sequence of the Southern Karavanks exhibits typical evolution of a passive continental margin with advancing extensional tectonics reaching its peak during the upper Late Devonian to lower Early Carboniferous (Diener, 2002).  Mainly neritic limestones and shallow marine shales had been depositing on the spreading rift-basin floor troughout the Late Ordovician, followed by Silurian to Middle Devonian pelagic limestones and deep marine shales inculding tuffs (Hubmann, 2014). As the shelf of the northward drifting Noric terrane entered the subtropical belt (31° in the Middle and 25 °in the Late Devonian (Schaetz, 2004))  the envirionmental conditions started to favor reef growth and carbonate platform formation. Pelagic sedimentation continuing into the Early Devonian prevailed until the late Emsian when shallow and deep-marine facies belts evolved over short distances in differentially subsiding basin affected by sinsedimetary extensional tectonics. Various rates of subsidence coupled by low sedimentatary rates offshore and condensation of pelagic deposits led to huge differences in thickness of proximal and distal units (Kreutzer et al., 1997; Schonlaub & Histon, 1999, 2000; see Humbann et al., 2014 for thickness of individual units). Thick reef and near-reef sediments were passing basinward into relatively thin pelagic cephalopod-limestones, shales and cherts. In shallow-marine setting an extensive carbonate platform was established which persisted up to the late Frasnian. Several hundred meters thick platform succession includes carbonate buildups whose core and reef-flat facies, dominated by tabulate corals, stromatoporids and green algae Renalcis, intefinger with forereef pack- and rudstones composed of the fragmented core-building organisms and with backreef limestones incuding algal bindstones containing sedimentary structures indicating inter-and supratidal environments (Rantitsch, 1992; McCann et al., 2008). Based on the local occurences of volcaniclastic material within the middle Devonian part of the complex, closely spaced facies belts, and supposed inter-reef mudstones  suggesting sdimentation between discrete reef-bodies, the reefal structures of the Southern Karavanks have been compared to present day atolls as opposed to the coeval barrier-type reefs of the Carnic Alps (Rantitsch, 1992; McCann et al., 2008, Schonlaub, 2013 and references therein). In both the Southern Karavanks and Carnic Alps synsedimentary extensional tectonics at the passive continental margin led to a basinal collapse causing drawning and cessation of reef growth by the late Frasnian, followed by uniform pelagic sedimentation of condensed cephalopod-bearing limestones and radiolarian cherts (lydites) continuing across the Devonian-Carboniferous border and lasting up to the lowermost Visean. (Schonlaub, 1992; Schonlaub & Histon, 1999; 2000; Ebner et al., 2010; Corradini et al., 2012, 2017). Similar pelagic sequences are widespread throughout the Galatian Superterrane as reflection of thermal subsidence of the blocks detached from the northern Gondwanan Margin, prior to their collison with the southern margin of Hanseatic terrane heralded by Tournaisian/Visean olistolith-bearing flysch sedimentation (von Raumer et al., 2013; Stampfli et al., 2013). The Late Devonian/Early Carboniferous deepening might also be related to flexure of the underriding plate approaching the subduction zone (Stampfli, 1996). As the geodynamic conditions changed in the Early Carboniferous from passive margin dominated by extensional tectonics to an active one, flexure of the underriding plate in response to its entry into the subduction zone caused a slow rise of surface seaward of the trench in a feature known as a forebulge (Schonlaub & Histon, 1999, 2000; Forke et al., 2006; Schonlaub & Forke, 2007) . The formation of the forebulge south of the incipient subduction zone resulted in relative sea level drop leading locally to karstification and erosion/non-deposition across the Devonian/Carboniferous boundary. The subaerial erosional gaps and paleorelief features spanning the Frasnian - late Tournasian/early Visean interval can be observed in the  goniatite-clymmenid bearing pelagic limestones and even atop of the underlying reefs (Tessensohn 1974; Schönlaub et al. 1991; Forke et al., 2006; Schonlaub & Forke, 2007; Ebner et al., 2008, McCann et al., 2008; Pondrelli et al., 2014). The foregoing has also been attributed to global glacial eustatic sea-level fluctuations at the Devonian-Carboniferous transition but given the spatialy-confined nature of the phenomena synsedimentary tectonics was probably a major factor (Ebner et al., 2008). The continous north-directed subducion lead to a diachronous flysch-like sedimentation of the 2000 m thick clastic Hochwipfel Formation of younger Visean to younger Moscowian age, marking the onset of the Variscan orogenic events in the eastern Carnic Alps and Southern Karavanks. (Hubich et al., 1999; Laufer et al., 2001; Deiner, 2002; Forke et al, 2006; Schonlaub & Forke, 2007). Older Ordovician to Early Carboniferous sediments incorporated into the accretionary wedge during the ongoing subduction were redeposited as olistolithes in course of the rapid turbidite, gravity mass flow, and slump sedimentation (Diener, 2002) in deeping trench (Hubich et al., 1999; Laufer et al., 2001; Forke et al, 2006; Schonlaub & Forke, 2007). The rapidly subsiding sedimentary basin is interprented by Diener (2002) as pull-apart basin at the strike-slip continental margin.

 

Post-Variscan Evolution (Late Carboniferous- Permian/Triassic boundary)

The post-Variscan i.e. late to post orogenic succession (Late Carboniferous-Late Permian) of the Southern Karavanks consists of two transgressional phases (tectono-sedimentary cycles) separated by unconformity caused by a phase of uplift and erosion.

 

The first cycle (Late Carboniferous - Early Permian)

The deformed Prevariscan basement including the synorogenic sediments of the Hocwipfel Formation is overlain in the eastern Carnic Alps and Southern Karavanks by the lowermost cycle consisting of deltaic and shallow marine silicilastic and carbonate sediments, deposited in discrete basins formed by block-and-wrench faulting subsequent to the final phase of the Variscan Orogeny (McCann et al., 2008 and references therein).

 

The Late Carboniferous - Early Permian sedimentary evolution of both regions is characterized by gradual shift of depositional setting from mixed siliciclastic-carbonate sedimentation on a coastal to shallow-marine ramp setting (Auernig Fm) towards open marine conditions with predominately carbonate sedimentation (Rattendorf Group), culminating in carbonate succession deposited on a rimmed shelf margin (Trogkofel Group) at the fringes of the Western Palaeo-Tethys. Starting from Early Asselian and at least up to the Late Sakmarian, the sedimentary evolution of the central Southern Karavanks was following a different path (see below).

 

The first cycle (Late Carboniferous-Early Permian), and the entire post-Variscan sequence of the eastern Carnic Alps for that matter, commences with Collendiaul Formation resting on the pre-Varisan basement with erosional unconformity caused by the Variscan uplift. Lydite breccias and conglomerates of the Collendiaul Formation resulting from the erosion of the uplifted area are lacking known exposures in the Southern Karavanks, hence the succession there commences with alternating fluvio-deltaic siliciclastic and shallow marine deposits of the Auernig Formation. (Forke et al, 2006; Schonlaub & Forke, 2007; Novak, 2007). The cyclic silicilastic-carbonate sedimentation-pattern has been largely attributed to glacioeustatic sea level oscilations (Massari & Venturini, 1990; Massari et al., 1991; Venturini 1990b; Krainer, 1991; 1992, Samankassou, 1997). Predominantly calcareous intervals reflect sea-level highstands with warmer average water temperature promoting carbonate production, while lowstands with cooler average water temperature hindered carbonate production resulting in deposits dominated by siliciclasts (Samankassou, 1997). The carbonate horizons are dominated by indistinctly bedded to massive limestones representing fossilized dasycladacean-mounds that thrieved at the transgressive-highstands. According to Buttersack & Boeckelman (1984) the controlling factor of algal growth has been variable siliclastic input associated with various rates of basinal subsiding: the high detrital influx during periods of intense subsidence suffocated algal growth and vice versa, resulting in alternating siliciclastic and calcareous horizons.

 

Fig.5: Idealized Auernig cyclothem from the upper part of the Auernig Formation (after Krainer & Davidov, 1998).

 

A cyclicity continued accros Carboniferous-Permian border  albeit with general transgression trend having more stable marine conditions, reflected in predominantely calcareous facies of the Rattedndorf Group formations (Forke, 2002; Corradini et al., 2012).

 

The carbonate-dominated Schulterkofel Formation of the Carnic Alps consists of 4 cyclothems, each starting with thin siliclastic horizon deposited in a nearshore environment during relative sea level lowstands.  Siliclastics at the base of each cyclothem  grade upwards into bedded fossiliferous and massive algal limestones accumulated during the trangressions. The massive limestones represent dasycladacean mounds, often capped by cherty limestones (s.c. »shroud facies«) indicating cessation of algal growth by drawning during sea level highstands (Samankassou, 1999; Forke, 2002; Samankassou, 2003; Novak, 2007; Kido et al., 2012). In sharp contrast to the mainly calcareous Schulterkofel formation of the Carnic Alps,  the majority of coeval exposures in the Southern Karavanks exhibit siliciclastic-dominated lithofacies (Novak, 2007), inferring that diachronous sedimentation of the Aeurnig Formation streched in the Southern Karavanks into the uppermost gzhelian is temporally overlapping with Schulterkofel formation of the Carnic Alps. Typical carbonate-dominated beds with shroud-veiled alagal mounds outcrop at the single exposure (1,5 cyclothem preserved) in the central S. Karavanks (Forke, 2002; Novak, 2007).

 

By the Asselian sedimentary evolution of the central and western Southern Karavanks diverged, with the later having common depositional history with the Carnic Alps. There, the mainly calcareous Rattendorf Group is intercalated with the siliciclastic horizon of Grenzland Formation deposited in a very shallow-marine environment with periodic subaerial exposures, evidenced by collapse breccias, paleosols and fractures (Forke et al., 2006, Schonlaub & Forke, 2007). However, outcrops often dubiously assigned to the Grenzland Formation  are scarce in the western Southern Karavanks (Novak, 2007).

 

During the ongoing deposition of the fossil-barren Grenzland Formation, the central Southern Karavanks apparently formed part of another domain with parallel but distinct sedimentation patterns.

 

In the middle to late Asselian the central Southern Karavanks undergone evolution of carbonate platform from a gently sloping, siliclastic(?) ramp to a reef-rimmed shelf, evidenced by the Dovžavova Soteska Formation. The lowermost, silicilastic part of the formation grades upwards with the increasing carbonate component share into the Dovžanova Soteska Limestone Member, representing reef mound structure dominated by encrusted skeletal grains embedded in micrite matrix. The reef mound progressively evolved into a rigid shelf-margin barrier through a series of rapid progradations alternating with backstep-coupled vertical accretions, the former corresponding to the sea-level standstills or slow rises and the latter to the rapid rises. Reef growth terminated by subaerial exposure recorded in erosional surface atop of the Dovžanova Soteska Limestone member was followed by transgression, which shifted depositional setting towards open-marine platform interior protected by ooilitic and sand shoals (= lagoon) and interspersed with rugose coral patch reefs. The calcareous-silicilastic open lagoon deposits, grouped into the Born Formation are in buried fault-contact with the informal Rigelj beds unit which reflects gradual seaward shift of facies belts, subsequently followed by a landward one. Depositional setting shifted from transitional coastal (clastic rocks), through inner-platform (algal limestones interbedded with clayshale) with restricted (low algal-diversity) and open marine conditions (high diversity), towards platform edge belt (reef limestones and limestone breccias), and vice versa. (Forke, 2002, Novak, 2007, Novak & Skaberne, 2007, Novak 2009).

 

The foregoing differences in Early Permian lithologic successions of the Carnic alps/western Southern Karavanks (Grenzland Fm) and the central Southern Karavanks (Dovžanova Soteska Fm, Born Fm, Rigelj beds) may reflect lateral facies variations in the Southern Alps, or the latter even represent independent tectonic unit (Forke, 2002).

 

Silicilcastic input, characterizing the mid-part of Rattendorf group (Grenzland Formation)  decreased by time of Zweikofel Formation, mainly deposited in carbonate inner-shelf environments with high-energy ooid barriers (Schonlaub & Forke, 2007; ; Krainer et al., 2009; Novak & Skaberne, 2009, Hubman et al., 2014).

 

In the Late Artinskian commenced sedimentation of the Trogkofel Group. By then the depositional-cyclicity typical of the Auernig Formation and to a lesser degree of the Rattendorf Group ceased yet the sea-level fluctuations, presumably recorded by multiple phases of karstification and subaerial exposure surfaces, may continued into the Trogkofel limestone  (Krainer et al, 2009). The carbonate succession of the Trogkofel Formation infers platform-reef-slope geometry. Its lithofacies types comprise dominant massive limestones representing shelf margin skeletal-microbial-cement reefs, bedded dasycladacean- and fusulinid-containing limestones deposited on platform behind shelf-margin reefs, and upper slope deposits (breccias) (Schonlaub & Forke, 2007; Hubmann et al., 2014; Schaffhauser et al., 2015). Downfaulting-induced landward shift of facies belts (backstep) led to juxtaposition of unbedded shelf-margin-buildup limestone atop of bedded platform limestones (Krainer et al, 2009). Deposition of the Trogkofel Formation was terminated by uplift related to transpressional ("Saalian") tectonic phase, resulting in subaerial truncation and karstification (Corradini et al., 2012; Schaffhauser et al., 2015).  

 

The emersion and subsequent erosion produced coarsely clastic rocks given various names (i.e. Tarvis breccia, Trogkofel conglomerate/breccia), depending on their lithology and underlaying basement (see Schonlaub & Forke, 2007; Hubmann et al, 2014). They supposedly represent rudite horizonts derived from Trogkofel limestone, albeit their composition varies and stratigraphic position remains unclear.

 

The second cycle (Middle - Late Permian)

Sedimentation of the continental rudite deposits, regulated by  newly commenced transpressional tectonic phase was followed by marine to terrigenous Gröden Formation, deposited in fluvial, playa and shallow water environments, and finally by basal evaporitic, lagoonal and shallow marine sediments of the Bellerophon Formation indicating slow rise of sealevel (Vozarova et al., 2009; Corradini et al, 2012).

 

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