Late Paleozoic reef mounds of the Carnic Alps (Austria/Italy)

Original article

Late Paleozoic reef mounds of the Carnic Alps (Austria/Italy)

Bioconstructions de type « reef mounds » dans le Paleozoıque

superieur des Alpes Carniques (Autriche/Italie)

Karl Krainer

Institute of Geology and Paleontology, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria

Received 1 June 2006; accepted 15 December 2006

Available online 15 August 2007

http://france.elsevier.com/direct/GEOBIO

Geobios 40 (2007) 625–643

Abstract

The Late Paleozoic (early Kasimovian–late Artinskian) sedimentary sequence of the Carnic Alps (Austria/Italy) is composed of

cyclic, shallow-marine, mixed siliciclastic–carbonate sedimentary rocks. It contains different types of skeletal mounds in different

stratigraphic levels. The oldest mounds occur at the base of the Auernig Group, within a transgressive sequence of the basal Meledis

Formation. These mounds are small and built by auloporid corals. Algal mounds are developed in the Auernig Formation of the Auernig

Group, forming biostromes, and Lower Pseudoschwagerina Limestone of the Rattendorf Group forming biostromes and bioherms. The

dominant mound-forming organism of these mounds is the dasycladacean alga Anthracoporella spectabilis. In mounds of the Auernig

Formation subordinately the ancestral corallinacean alga Archaeolithophyllum missouriense is present, whereas in mounds of the Lower

Pseudoschwagerina Limestone a few calcisponges and phylloid algae occur locally at the base and on top of some Anthracoporella mounds.

Mounds of the Auernig Formation formed during relative sea level highstands whereas mounds of the Lower Pseudoschwagerina Limestone

formed during transgression. The depositional environment was in the shallow marine, low-turbulence photic zone, just below the active

wave base and lacking siliciclastic influx. The algal mounds of the Carnic Alps differ significantly from all other algal mounds in composition,

structure, zonation and diagenesis; the formation of the mounds cannot be explained by the model proposed by Wilson (1975). The

largest mounds occur in the Trogkofel Limestone, they are composed of Tubiphytes/Archaeolithoporella boundstone, which shows some

similarities to the ‘‘Tubiphytes thickets’’ of stage 2 of the massive Capitan reef complex of the Guadalupe Mountains of New Mexico/West

Texas.

# 2007 Elsevier Masson SAS. All rights reserved.

Resume

Le Paleozoıque superieur (Kassimovien inferieur–Artinskien superieur) des Alpes Carniques (Autriche/Italie) est compose d’une serie

sedimentaire mixte siliciclastique et carbonatee, cyclique, de mer peu profonde. Cet ensemble contient differents types de bioconstructions

(« skeletal mounds ») a differents niveaux. Les plus anciens monticules bioconstruits sont situes a la base du groupe d’Auernig, dans une

sequence transgressive de la formation de Meledis basale. De taille modeste, ils sont edifies par des tabules auloporides. Des biostromes

algaires sont frequents dans la formation d’Auernig du groupe eponyme et dans le Calcaire inferieur a Pseudoschwagerina du groupe de

Rattendorf, a la fois sous forme de biostromes et de biohermes. Le principal organisme constructeur est la dasycladale seletonellacee

Anthracoporella spectabilis. Dans la formation d’Auernig, des algues corallines ancestrales Archaeolithophyllum missouriense leur sont

subordonnees, tandis que dans le Calcaire inferieur a Pseudoschwagerina, quelques calcisponges et de rares algues phylloıdes les

accompagnent localement, a la base et au sommet de certains edifices. Les monticules de la formation d’Auernig se sont formes lors de

hauts-niveaux marins relatifs, alors que ceux de l’autre formation ont pris naissance durant des transgressions. L’environnement de depot etait

situe en mer peu profonde, dans la zone photique, loin des apports siliciclastiques et en eaux faiblement agitees, juste sous la limite d’action

des vagues. Les bioconstructions algaires des Alpes Carniques different nettement des autres monticules de ce type, par leur composition,

leur structure, leur zonation et leur diagenese ; leur formation ne peut donc pas etre expliquee par le modele propose par Wilson (1975). Les

plus grands monticules bioconstruits se rencontrent dans le Calcaire de Trogkofel. Ils sont composes de boundstones a Tubiphytes/

E-mail address: [email protected].

0016-6995/$ – see front matter # 2007 Elsevier Masson SAS. All rights reserved.

doi:10.1016/j.geobios.2006.12.004

mailto:[email protected]

http://dx.doi.org/10.1016/j.geobios.2006.12.004

K. Krainer / Geobios 40 (2007) 625–643626

Archaeolithoporella qui ne sont pas sans rappeler les « Tubiphytes thickets » du stade 2 du complexe recifal du Capitan dans les monts de

Guadalupe (Nouveau Mexique et Texas occidental, Etats-Unis).

# 2007 Elsevier Masson SAS. All rights reserved.

Keywords: Late Paleozoic; Mounds; Auloporid corals; Anthracoporella; Tubiphytes; Archaeolithoporella

Mots cles : Paleozoıque superieur ; Monticules bioconstruits ; Tabules auloporides ; Anthracoporella ; Tubiphytes ; Archaeolithoporella

1. Introduction

Most of Late Paleozoic organic buildups are mounds (reef

mounds). The dominant mound-building organisms of Upper

Carboniferous/Lower Permian mounds are phylloid algae (red

and green algae) such as Ivanovia, Eugonophyllum, Anchico-

dium, Archaeolithophyllum, the enigmatic/problematic alga

Archaeolithoporella, and the enigmatic platy organism Palaeoa-

plysina associated with Tubiphytes (summaries in West, 1988;

James and Bourque, 1992; Wahlman, 2002). Tubiphytes has been

revised by Riding (1993) and its correct name is Shamovella. But

as the term Tubiphytes is still more popular, it is also used in this

paper. Mounds constructed by non-phylloid dasycladacean and

codiacean algae are rare. They are reported from the

Mississippian of Nova Scotia and the Arctic Archipelago of

Canada, where they occur associated with corals and bryozoans

(Davies et al., 1989).

Mounds are defined as structures, which were built by

smaller, commonly delicate and/or solitary elements in tranquil

settings (James and Bourque, 1992). Three types of mounds are

differentiated: organically controlled (a) microbial; (b) skeletal

mounds (also called biogenic mounds), and (c) mud mounds

Fig. 1. Simplified geologic map of the central Carnic Alps with locations of the Lat

Kronalpe (Auernig Fm.); 4 Schulterkofel; 5 Ringmauer (Lower Pseudoschwagerin

Fig. 1. Carte geologique simplifiee du centre des Alpes Carniques montrant l’empl

Puartis (formation de Bombaso) ; 2 Garnitzenberg ; 3 Kronalpe (formation d’Auerni

Zweikofel ; 7 Trogkofel (Calcaire de Trogkofel).

which were formed by inorganic accumulation of lime mud

with variable amounts of fossils.

In skeletal mounds the skeletal builders, that is bryozoans,

skeletal algae and sponges, acted as bafflers, trappers, binders

and stabilizers.

In the Late Paleozoic sequence of the Carnic Alps all

mounds are skeletal mounds with auloporid corals and skeletal

algae (particularly Anthracoporella) being the dominant mound

building-organisms (overview by Samankassou, 2003).

The aim of the present paper is to summarize the present

knowledge of the Late Paleozoic mounds of the Carnic Alps

mostly based on author’s published data, which are comple-

mented by results of recent investigations.

2. Geological setting and stratigraphy

In the Carnic Alps, an east–west-trending mountain chain in

Southern Austria along the Austrian–Italian border, Late

Carboniferous–Early Permian sedimentary rocks are well

exposed (Fig. 1). They unconformably overlie the deformed

Variscan Basement, which consists of folded and faulted Early

e Paleozoic mounds: 1 Cima Val di Puartis (Bombaso Fm.); 2 Garnitzenberg; 3a Limestone); 6 Zweikofel; 7 Trogkofel (Trogkofel Limestone).

acement des monticules bioconstruits du Paleozoıque superieur. 1 Cima Val di

g) ; 4 Schulterkofel ; 5 Ringmauer (Calcaire inferieur a Pseudoschwagerina) ; 6

Fig. 3. Idealised ‘‘Auernig Cyclothem’’ from the upper part of the Auernig

Group (Auernig Formation) in the Garnitzenberg – Kronalpe area.

Fig. 3. « Cyclotheme d’Auernig » virtuel dans la partie superieure du groupe

d’Auernig (formation d’Auernig) du secteur de Garnitzenberg-Kronalpe.

Fig. 2. Stratigraphy of the Late Carboniferous–Early Permian sedimentary

sequence in the Carnic Alps. The formations containing mounds are marked by

asterisks.

Fig. 2. Stratigraphie de la serie sedimentaire du Carbonifere superieur–Permien

inferieur des Alpes Carniques. Les formations contenant des monticules

bioconstruits sont marquees par des asterisques.

K. Krainer / Geobios 40 (2007) 625–643 627

Paleozoic, deep- to shallow-marine carbonate, siliceous, and

siliciclastic sedimentary rocks.

Subsequent to the Variscan Orogeny, with its climax during

the Westphalian (i.e., late Bashkirian–Moscovian), sedimentary

basins formed due to extensional tectonics causing block- and

wrench-faulting (Venturini, 1982, 1990a, 1990b).

A thick sequence of deltaic and mostly shallow marine,

mixed siliciclastic–carbonate sediments accumulated in these

basins. The sequence is subdivided into Bombaso Formation,

Auernig Group, Rattendorf Group, and Trogkofel Group from

base to top (Fig. 2).

2.1. Bombaso Formation

The Bombaso Formation ranges in thickness from a few to

about 200 m and consists of poorly sorted, immature breccias

and conglomerates which are composed of either predomi-

nantly radiolarian chert and volcanic clasts (Pramollo Member)

or of Silurian–Devonian carbonate clasts (Malinfier Horizon),

all derived from the underlying Variscan basement.

The succession is a fining upward sequence. Rare brachio-

pods, crinoids and fusulinids indicate deposition in a marine

environment (Venturini, 1989, 1990a, 1990b; Krainer, 1990,

1992). Fusulinids and plant fossils indicate late Moscovian to

early Kasimovian (Cantabrian) age (Kahler, 1983, 1985, 1986,

1989; Fritz and Krainer, 1995; Krainer and Davydov, 1998;

Davydov and Krainer, 1999; Forke and Samankassou, 2000).

2.2. Auernig Group

The Auernig Group is up to 1200 m thick and consists of

alternating siliciclastic and carbonate sedimentary rocks. The

sequence is divided into the Meledis (dominantly siliciclastic),

Pizzul (mixed siliciclastic–carbonate), Corona (dominantly

siliciclastic), Auernig (mixed siliciclastic–carbonate) and

Carnizza Formations (dominantly siliciclastic) according to

Selli (1963) and corresponding to ‘‘untere kalkarme, untere

kalkreiche, mittlere kalkarme, obere kalkreiche und obere

kalkarme Schichtgruppe’’ of the German literature (e.g. Kahler

and Metz in Kuehn, 1962). Based on fusulinids and megaplant

fossils, the Auernig Group is of Kasimovian to early

Orenburgian (Stephanian) age (Fritz et al., 1990; Krainer

and Davydov, 1998) (Fig. 2).

Particularly in the upper part (Corona, Auernig and Carnizza

Formations) mixed siliciclastic–carbonate, high frequency

cycles (‘‘Auernig Cyclothems’’) are well developed.

A typical Auernig Cyclothem is composed of the following

lithofacies (from base to top; Fig. 3):

(a) q
uartz-rich conglomerates of a nearshore facies at the base;
(b) c
oarse-grained, trough-cross-bedded sandstones of the
upper shoreface;


(c) fi
ne-grained, hummocky-cross-bedded sandstones of the
lower shoreface;

(d) i
nterbedded with siltstone and shale, locally bioturbated
and containing diverse fossils;

(e) b
edded to massive, fossiliferous limestones of a shallow
marine environment. The massive limestone facies repre-

sents algal mounds.

This succession is a transgressive sequence, which is

overlain by a regressive sequence composed of shale and

siltstone (d), hummocky-cross-bedded and trough-cross-

bedded sandstones (c and b), the latter are erosively overlain

by quartz-rich conglomerates (a), which form the base of the

next cycle. The thickness of these Auernig Cyclothems

measures 10–40 m. Conglomerates were deposited during

relative sea level lowstands, the fossiliferous limestones

accumulated during relative sea level highstands. The forma-

tion of the Auernig Cyclothems is related to glacio-eustatic sea

level changes caused by Gondwana glaciation (for details see

Selli, 1963; Venturini, 1982, 1990a, 1990b, 1991; Kahler, 1983,

1985, 1986, 1989; Buttersack and Boeckelmann, 1984;

Boeckelmann, 1985; Krainer, 1990, 1991, 1992, 1995; Massari

and Venturini, 1990; Massari et al., 1991; Flugel et al., 1997;

Krainer and Davydov, 1998).

2.3. Rattendorf Group

The sedimentary rocks of the Auernig Group are con-

formably overlain by sedimentary rocks of the Rattendorf

Group which is approximately 450 m thick and divided into

Lower Pseudoschwagerina Limestone (Schulterkofel Forma-

tion), Grenzland Formation and Upper Pseudoschwagerina

Limestone (Zweikofel Formation) from base to top (Fig. 2).

The Lower Pseudoschwagerina Limestone is up to 160 m

thick and consists of fossiliferous limestones with thin

siliciclastic intercalations forming three well developed deposi-

tional cycles (see Flugel, 1968, 1974; Homann, 1969, 1972;

Kahler and Krainer, 1993; Flugel et al., 1997; Samankassou,

1997; Forke et al., 1998). Clastic sediments form the base of all

depositional cycles and were deposited during relative sea level

lowstands in a shallow marine, nearshore environment. Well-

bedded fossiliferous limestones and massive algal mounds

accumulated during transgression and thin intervals of dark gray,

bedded cherty limestones represent deposits of relative sea level

highstands with water depths of some tens of meters. According

to Flugel (1974) sediments of the Lower Pseudoschwagerina

Limestone were deposited in a nearshore shallow marine

environment of a morphologically and bathymetrically differ-

entiated tide-free inner shelf.

The fusulinid fauna points to late Orenburgian to earliest

Asselian age, the C/P boundary lies within the uppermost part

of the Lower Pseudoschwagerina Limestone (Kahler and

Krainer, 1993; Forke et al., 1998; Krainer and Davydov, 1998;

Forke, 2002).

The Grenzland Formation has a maximum thickness of

125 m and is a cyclic, dominantly siliciclastic sequence

composed of shallow marine, quartz-rich conglomerates,

sandstones, siltstones and shales, and intercalated thin, bedded

fossiliferous limestones (Tietz, 1974; Buggisch et al., 1976;

Buttersack and Boeckelmann, 1984; Boeckelmann, 1985). Thin

shale horizons contain plant fossils (Fritz and Boersma, 1984;

Boersma and Fritz, 1990), the fusulinid assemblage of the

limestones indicates middle/late Asselian age (Kahler, 1985,

1986; Forke, 1995; Krainer and Davydov, 1998).

The Upper Pseudoschwagerina Limestone is up to 170 m

thick and consists of a cyclic succession of dark-grey, thin-

bedded fossiliferous limestones, thin intercalations of siltstone

and sandstone, and rare fine-grained conglomerates. The well

developed cycles are interpreted as the result of repeated

shifting from nearshore to offshore environments in an open

marine shelf lagoon (Flugel, 1968, 1971, 1977, 1981; Flugel

et al., 1971, 1997; Homann, 1969, 1972; Buttersack and

Boeckelmann, 1984; Forke, 1995; Vachard and Krainer,

2001b). Kahler (1985) and Krainer and Davydov (1998) dated

the Upper Pseudoschwagerina Limestone as late Asselian,

whereas Forke (1995, 2002) considered it to be Sakmarian.

2.4. Trogkofel Group

Sediments of the Rattendorf Group are overlain by a 400 m

thick sequence of thick-bedded and massive limestones of the

Trogkofel Group (including Trogkofel Limestone, Treßdorf

limestone and Goggau limestone; Fig. 2). The type locality is

the Trogkofel massif in the central Carnic Alps. The Trogkofel

Group was studied in detail by Buggisch (1980), Buggisch and

Flugel (1980), Flugel (1980, 1981), Flugel and Flugel-Kahler

(1980), Kahler and Kahler (1980). Sediments of the Trogkofel

Group accumulated in shallow, restricted and open marine

shelf lagoons with only minor bathymetrical differences.

Shelf-edge carbonates are represented by Tubiphytes/Archae-

olithoporella buildups (Flugel, 1980). The limestones contain

a diverse assemblage of calcareous algae (46 species; Flugel

and Flugel-Kahler, 1980) and fusulinids (about 70 species;

Kahler and Kahler, 1980). Based on fusulinids, the Trogkofel

Group ranges in age from Sakmarian to late Artinskian (Kahler

and Kahler, 1980; Kahler, 1986; see also Krainer and Davydov,

1998).

The Trogkofel Group is unconformably overlain by the

Tarvis Breccia, which was formed by intense block faulting

(‘‘Saalian movements’’) during the Kungurian (Kahler, 1980).

3. Mounds of the Auernig Group

Within the thick succession of the Auernig Group mounds

occur in the lowermost part of the Meledis Formation and in

thicker limestone horizons of the Auernig Formation (Fig. 2).

Mounds of the Meledis Formation are formed of auloporid

corals whereas in the Auernig Formation the mound-building

organisms are calcareous algae.

3.1. Auloporid coral mounds of the Meledis Formation

Small mounds of auloporid corals occur within a

transgressive sequence in the lowermost part of the early


Kasimovian Meledis Formation near Cima Val di Puartis

(details in Flugel and Krainer, 1992). The sequence rests on a

thin interval of the Bombaso Formation and is composed of

dark grey shales with intercalations of fine-grained conglom-

erates and calcareous sandstone beds in the lowermost part, and

siltstones, algal limestones and small auloporid coral mounds in

the upper part. The number and diversity of fossils increases

from base to top. The exposed thickness is about 10 m (Fig. 4).

Two mounds were investigated in detail in Flugel and

Krainer (1992); both are lens-shaped and embedded in silty

shale. Mound A is 30 cm thick and 90 cm wide (Figs. 4 and 5),

Mound B is 20 cm in thickness and 80 cm in width (Fig. 6).

Mound A interfingers with the adjacent shale, Mound B does

not. Mound A rests on silty shale, whereas Mound B is

Fig. 4. Stratigraphic column of the Bombaso Formation and basal Meledis

Formation near Cima Val di Puartis SW of Straniger Alpe, containing an

auloporid coral mound in the upper part of the section (location see Fig. 1).

Fig. 4. Colonne stratigraphique de la formation de Bombaso et de la formation

Meledis basale, pres de la Cima Val di Puartis, au S.O. de Straniger Alpe. Une

bioconstruction a auloporides apparaıt dans la partie superieure de la coupe

(voir sa localisation sur la Fig. 1).

developed on shale containing densely packed brachiopod

shells forming a hard bottom.

Two types of matrix are recognized in the mounds: type (a)

consists of dark homogenous micrite containing bioclasts

(ostracods, smaller foraminifers, fusulinids, gastropods, echi-

noderms and spicule-like bioclasts) and type (b) is grey

inhomogenous calcareous siltite containing fewer bioclasts

than type (a). Type (a) micrite is interpreted to represent

autochthonous sediment and type (b) is interpreted as

allochthonous sediment.

The mound-forming organisms are phaceloid tabulate corals

(Multithecopora: order Auloporida) occurring in life position

with upward branching, delicate growth forms (Fig. 7).

Chaetetids are rare.

The position of the mounds within the transgressive

sequence indicates that mound growth started at the maximum

flooding surface during the early highstand systems tract, i.e.

during absence of coarse clastic influx, but with low

sedimentation rate and pronounced low-energy conditions.

Mound growth was stopped by the change from higher

turbulence to quiet water and the deposition of fine-grained

capping beds.

Similar small auloporid coral mounds up to 5 cm high and

15 cm in diameter are also present in the middle of the

lowermost limestone horizon of the basal Meledis Formation

southwest of Zollnersee (Davydov and Krainer, 1999). There

the mounds also occur within a transgressive sequence, mound

formation started during an early phase of highstand.

3.2. Algal mounds of the Auernig Formation

Within the Auernig Formation, mounds are present in the

lower part of the sequence particularly in the basal limestone

horizon at the localities Gugga/Garnitzenberg and Kronalpe

(Fig. 8). These mounds were studied in detail by Krainer

(1995).

The basal limestone horizon of the Auernig Formation is up

to 16 m thick and consists of well-bedded fossiliferous

limestone and massive limestone which locally occur in the

central part of the limestone successions. The limestone

horizon is part of a well developed transgressive cyclothem

(‘‘Auernig Cyclothem’’). The well-bedded limestone facies

displays bed thicknesses mostly of 5–20 cm, rarely up to 40 cm,

and consists of the following microfacies (Fig. 8):

� b
ioclastic wackestone/packstone;
� f
usulinid wackestone/packstone;
� A
nthracoporella wackestone/packstone;
� A
rchaeolithophyllum bindstone/bafflestone;
� A
nthracoporella bindstone/bafflestone;
� A
nthracoporella packstone/rudstone;
� b
ioclastic mudstone;
� b
indstone;
� b
ioclastic siltstone/fine-grained sandstone.
The massive limestones of the mound facies are light grey,

up to 4 m thick and extend laterally over several tens of meters.

Fig. 5. Auloporid mound A (Cima Val di Puartis) interfingering with silty shale (left). Height of the mound is approximately 30 cm. Position of the mound within the

sequence is shown in Fig. 4.

Fig. 5. Bioconstruction A a auloporides (Cima Val di Puartis) interdigitee dans des argilites silteuses (a gauche). Sa hauteur est d’environ 30 cm ; sa place dans la

sequence est indiquee sur la Fig. 4.


At Kronalpe they are more than 100 m wide and form very flat

biostromal buildups.

From the mound facies the following microfacies have been

determined:

Fig. 6. Auloporid mound B (Rio Malinfier), embedded in marly sediments containi

20 cm (from Flugel and Krainer, 1992: Fig. 6b).

Fig. 6. Bioconstruction B a auloporides (Rio Malinfier), emballee dans des sedim

Hauteur approximative du monticule : 20 cm (d’apres Flugel et Krainer, 1992 : Fi

� A

ng

en

g.

nthracoporella bafflestone/bindstone;

� A
nthracoporella wackestone/bindstone;
� A
nthracoporella grainstone (rare);
� b
ioclastic wackestone (rare);
abundant brachiopod shell fragments. Height of the mound is approximately

ts marneux contenant d’abondants fragments de coquilles de brachiopodes.

6b).

Fig. 7. Thin section photograph of the auloporid mound facies showing auloporid corals in growth position, embedded in dark grey, fine-grained, locally silty matrix.

Sample VP 13, mound A, width of photograph 15 mm (Cima Val di Puartis).

Fig. 7. Photographie d’une lame mince du monticule de la Fig. 5, montrant les auloporides en position de vie, enchasses dans une matrice gris fonce, finement grenue

et localement silteuse. Echantillon VP 13, monticule A, largeur de la photographie : 15 mm (Cima Val di Puartis).


� f
usulinid wackestone/packstone (very rare).
Anthracoporella bafflestone/bindstone (Figs. 9 and 10)

consists of large, mostly unbroken algal thalli of Anthracopor-

ella spectabilis. The algal thalli are frequently found in growth

position; others are toppled in situ. The matrix is inhomogenous

micrite and pelmicrite containing only a few small bioclasts.

Binding organisms are sessile foraminifers, Archaeolithophyl-

lum lamellosum, Ungdarella and Girvanella.

In Anthracoporella wackestones/boundstones the algal thalli

toppled in situ or were transported only short distances. The

matrix is micrite and pelmicrite. Bioclasts, particularly

Anthracoporella, locally are encrusted by binding organisms

such as smaller foraminifers, Tubiphytes and algal crusts.

Anthracoporella grainstone, composed of broken, transported

algal thalli, and high contents of calcite cement, is rare.

The most abundant biotic constituents of the bedded

intermound and massive mound facies are calcareous algae,

particularly the dasycladacean alga Anthracoporella spect-

abilis. Epimastopora alpina is also present but less abundant.

Of some importance is the ancestral coralline alga Archae-

olithophyllum missouriense (Fig. 11). Other algae like

Pseudoepimastopora, Eugonophyllum, Gyroporella, Mizzia,

Anchicodium, Neoanchicodium, Globuliferoporella, and

pseudo-algae like Ungdarella, Efluegelia, Beresella, Nostocites

and Claracrusta rarely occur (Vachard and Krainer, 2001a).

Tubiphytes is present in all samples and may be abundant in the

mound facies. Fusulinids are frequent in the bedded limestones

but rare in the mound facies. Smaller foraminifers are common

in all facies (Vachard and Krainer, 2001a). Other bioclasts

include bryozoans, brachiopods, bivalves, gastropods, echino-

derms, calcisponges, ostracods and very rare small solitary

corals.

The massive mound facies is under- and overlain by well-

bedded, fossiliferous limestones. The mounds lack any vertical

or horizontal zonation. Anthracoporella spectabilis frequently

occurs in growth position forming Anthracoporella bafflestone/

boundstone. Pores between the algal thalli are almost

completely filled with micrite and pelmicrite.

Krainer (1995) interpreted Anthracoporella spectabilis to be

a member of the baffler guild. Because most of the lime mud

between the algal thalli probably formed in situ, partly as

‘‘automicrite’’ (microbially formed micrite), this facies

represents a boundstone rather than a bafflestone as noted by

Samankassou (1998).

The mounds formed during relative sea level highstands

lacking clastic influx in a shallow shelf environment within the

photic zone below the active wave base under quiet water

conditions, probably on a gently inclined ramp (Krainer, 1995).

Mound growth was stopped by a slight drop in sea level causing

more agitated water, in which bedded, fossiliferous limestones,

particularly different types of bioclastic wackestones, accu-

mulated.

The formation of these Anthracoporella mounds cannot be

explained by the model proposed by Wilson (1975).

4. Algal mounds of the Lower PseudoschwagerinaLimestone (Rattendorf Group)

Algal mounds are exposed in the lower part of the Lower

Pseudoschwagerina Limestone. Flugel (1987) was the first to

report algal mounds from the Ringmauer, which occur in

Fig. 8. Stratigraphic section through a transgressive sequence of an Auernig

Cyclothem at Kronalpe (location 3 on Fig. 1) with a massive algal mound within

the early highstand systems tract (EHST) in the middle of the limestone

succession (from Krainer, 1995: Fig. 6).

Fig. 8. Coupe stratigraphique a travers une sequence transgressive d’un

Cyclotheme d’Auernig a Kronalpe (localite 3 sur la Fig. 1) avec un monticule

algaire massif a l’interieur d’un cortege de haut niveau marin initial (EHST) au

milieu d’une succession calcaire (d’apres Krainer, 1995 : Fig. 6).


depositional cycles 2 and 3. There, the mounds form bioherms

and biostromes; they are 2–20 m, mostly around 3 m thick.

Based on a detailed microfacies analysis Flugel (1987)

distinguished three types of mounds:

� h
omogenous mounds composed of bioclastic wackestones
with abundant shell fragments, small Tubiphytes, foramini-

fers, gastropods and Anthracoporella;

� m
ounds consisting of bioclastic wackestones and packstones,
rare fusulinid and oolithic grainstones in the lower part and

Anthracoporella wackestones, rare oncoidal limestones and

bryozoan bindstones in the upper part;

� m
ounds composed of Anthracoporella wackestones at the
base, overlain by bioclastic wackestones containing phylloi-

dal algae, superposed by Anthracoporella varied wackes-

tones; some consisting of densely packed shell debris, others

composed of sponge spicules, and still others contain

Anthracoporella, brachiopods and sessile foraminifers.

The most abundant organisms of the mound facies are

dasycladacean algae (Anthracoporella spectabilis), brachio-

pods, sediment binding organisms, encrusting foraminifers,

Tubiphytes and encrusting algae.

According to Flugel (1987) the micritic matrix is formed by

in situ accumulation (?decay of algal thalli) rather than by

baffling of lime mud. Growth of the mounds probably started on

bioclastic and oolithic shoals and was influenced by the change

from soft to hard bottom. Flugel (1987) noted that the mounds

do not show any shallowing upward trend and in contrast to

many of the Late Paleozoic mounds of North America, there are

no indications of subaerial exposure. The bedded intermound

facies consists mostly of different types of bioclastic

wackestones containing abundant algal fragments (phylloid

algae and Anthracoporella).

These Anthracoporella mounds, which are overlain by dark,

thin-bedded cherty limestones of a deeper-water environment,

were drowned by a relative rise of sea level (Samankassou,

1999).

The most spectacular mounds of the Lower Pseudoschwa-

gerina Limestone occur in the steep northwestern flank of the

Schulterkofel (Fig. 12). These mounds are developed within a

prominent deepening upward sequence (depositional sequence

1) of the Lower Pseudoschwagerina Limestone.

Sequence 1 is composed of a 15 m thick conglomerate

succession with thin sandstone intercalations at the base, which

represent the uppermost part of the Carnizza Formation

(Auernig Group). The conglomerates and sandstones are

massive or display crude horizontal stratification; in a few beds

cross-bedding was observed. The intercalated sandstone layers

are horizontally laminated or hummocky cross-bedded. Trace

fossils occur on bedding planes. This coarse-grained succession

is overlain by thin sandstones, which grade into fine-grained

fossiliferous carbonate sandstones (oolitic grainstone), which

mark the base of the Lower Pseudoschwagerina Limestone.

Superposed is a 2 m thick sequence of thin-bedded, dark grey

micritic limestone composed of bioclastic wackestone and

fusulinid wackestone, packstone and grainstone. These bedded

limestones are overlain by massive, partly dolomitized lime-

stone up to 30 m thick, representing a large algal mound

composed mostly of Anthracoporella wackestone and bind-

stone. The mound is overlain by thin-bedded limestone

(bioclastic wackestone and grainstone, algal wackestone) of

the intermound facies with smaller algal mounds intercalated in

a distinct horizon (described below). Mound and intermound

facies are overlain by 4 m of thin-bedded, dark grey cherty

limestone with thin shale partings, grading upwards into 17 m

of bedded fossiliferous limestone and massive limestone (algal

mounds; see Fig. 12).

Superposed is a 8.5 m thick horizon of fine-grained

sandstone and siltstone with thin intercalations of fossiliferous

limestone beds. This dominantly clastic horizon represents the

base of depositional sequence 2.

The clastic sediments at the base of depositional sequence 1

are interpreted to have been deposited during a relative sea level

lowstand with high clastic influx, representing the lowstand

Fig. 9. Algal limestone from the mound facies at Kronalpe (Auernig Formation), composed of large Anthracoporella-thalli, many in growth position, and micritic

matrix. Pencil for scale.

Fig. 9. Calcaire a algues provenant d’une bioconstruction de Kronalpe (formation d’Auernig), qui se compose de grands thalles d’Anthracoporella, dont beaucoup

sont en position de vie, et d’une matrice micritique. Le crayon donne l’echelle.


systems tract (LST). Structural and textural features indicate a

shallow marine, nearshore environment (shoreface). The

overlying oolitic grainstones accumulated during the beginning

transgression in shallow, agitated water, marking the base of the

transgressive systems tract (TST). Bedded limestones of the

Fig. 10. Anthracoporella bafflestone/boundstone with unbroken thalli of Anthrac

photograph 18 mm (Auernig Formation, Kronalpe).

Fig. 10. Bafflestone/boundstone a Anthracoporella montant des thalles intacts d

pelloıdale. Largeur de la photographie : 18 mm (formation d’Auernig, Kronalpe).

intermound facies and massive limestones of the algal mound

facies formed in a shallow marine environment near or slightly

below the active wave base during transgression are thus

interpreted as the transgressive systems tract (TST). Cherty

limestones are assumed to have been deposited during a relative

oporella spectabilis embedded in micritic, locally pelletal matrix. Width of

’Anthracoporella spectabilis inclus dans une matrice micritique localement

Fig. 11. Archaeolithophyllum bafflestone/boundstone with large, unbroken thalli of A. missouriense in growth position, acting as bafflers. Matrix is fine lime mud

containing a few small bioclasts. Width of photograph 18 mm (Auernig Formation, Kronalpe).

Fig. 11. Bafflestone/boundstone a Archaeolithophyllum avec de grands thalles intacts d’A. missouriense en position de vie, jouant un role de capteurs de boue

carbonatee (« bafflers »). La matrice est une boue calcaire fine contenant quelques bioclastes. Largeur de la photographie : 18 mm (formation d’Auernig, Kronalpe).


sea level highstand with water depths of some tens of meters,

representing the highstand systems tract (HST) (see Saman-

kassou, 1999).

Two mounds have been studied in detail (Krainer et al.,

2003). Mound I is 6 m thick, the exposed width is 12 m. Mound

II measures 5.5 m in thickness and 11 m in width (Figs. 13 and

14).

Both mounds are asymmetrical in shape with the western

flank being steeper than the eastern flank. The boundary

between the mound and intermound facies is sharp.

The intermound facies is thin-bedded (5–15 cm) dark grey

limestone with thin shale partings. Limestone beds lap onto the

mound facies and are inclined off the mound, indicating a

primary positive topographic relief between the mound and

intermound facies of 1.5–2 m (Fig. 15).

The most abundant microfacies of the intermound facies is

phylloid algal wackestone/packstone containing abundant

recrystallized broken fragments of Eugonophyllum, subordi-

nate Anthracoporella and Epimastopora. Some of the algal

fragments are encrusted by Tubiphytes, smaller foraminifers,

bryozoans and encrusting algae such as Efluegelia, Ungdarella.

Gastropods, brachiopods, fusulinids, and echinoderms, ostra-

cods, rare solitary corals and calcisponges are present. The

matrix is micrite; rare small pores filled with calcite cement

occur. Subordinate are Anthracoporella wackestone, bioclastic

wackestone/packstone, bioclastic siltstone locally rich in

smaller foraminifers, and calcareous siltstone.

In the massive mound facies a poorly developed zonation is

observed. At the base boundstones composed of calcisponges

and a few bryozoans, bound by encrusting algae, Tubiphytes

and smaller foraminifers are developed. The core facies

dominantly consists of Anthracoporella boundstone and

subordinate algal wackestone (Fig. 16). Anthracoporella

boundstone consists of up to 4 cm large, upright algal thalli,

which are frequently still in growth position forming small

‘‘Anthracoporella bushes’’. The algal thalli are slightly

encrusted by Tubiphytes, encrusting algae, and sessile

foraminifers. Other bioclasts including bryozoans, calcis-

ponges, fusulinids, smaller foraminifers, echinoderms, gastro-

pods and ostracods are rare.

In areas where the algal thalli are densely packed and formed

algal bushes, pore space is mostly filled with calcite cement

(Fig. 16), whereas in less densely packed domains space

between the algal thalli is filled with different types of matrix:

(a) dark grey micrite containing a few small bioclasts and (b)

light grey peloidal micrite lacking small bioclasts, locally

displaying graded bedding. This type may grade into (c)

pelmicrosparite composed of small peloids, a few small

bioclasts and microsparitic cement. Peloidal micrite and

pelmicrosparite are younger than the dark grey micrite.

Within the core facies algal wackestones are subordinate.

They are composed mostly of broken fragments of phylloid

algae, Anthracoporella and Epimastopora, among other

bioclasts (Fig. 17).

The uppermost part of the massive mound facies consists of

phylloid algal bafflestone/bindstone, Anthracoporella bindstone,

Tubiphytes bindstone locally containing calcisponges, and

phylloid algal wackestone. There is a sharp boundary between

the mound facies and the overlying wackestones and packstones

of the bedded intermound facies. These mounds formed in a

similar environment to that of the Auernig Formation, that is, in

a shallow marine, low-energy environment free of clastic

Fig. 12. Stratigraphic section through the uppermost part of the Carnizza

Formation (Auernig Group) and lower part (depositional sequence 1) of the

Lower Pseudoschwagerina Limestone at Schulterkofel (locality 4 on Fig. 1)

with position of the algal mounds (arrow) within the upper part of a transgres-

sive systems tract (TST). LST = lowstand systems tract, HST = highstand

systems tract.

Fig. 12. Coupe stratigraphique dans la partie terminale de la formation de

Carnizza (groupe d’Auernig) et de la partie inferieure (sequence de depot 1) du

Calcaire inferieur a Pseudoschwagerina a Schulterkofel (localite 4 sur la Fig. 1)

avec l’emplacement des bioconstructions algaires (fleche) dans la partie super-

ieure d’un cortege transgressif (TST). LST = cortege de bas-niveau marin,

HST = cortege de haut-niveau marin.


influx within the photic zone in water depths not more than about

12 m.

5. Tubiphytes/Archaeolithoporella mounds of the

Trogkofel Limestone

The Trogkofel Limestone is composed of well-bedded

limestone and massive, frequently dolomitized limestone. The

bedded limestones are similar to those of the Upper

Pseudoschwagerina Limestone. At the Trogkofel, the massive

facies overlies a thick-bedded limestone sequence (Fig. 18),

and consists mostly of Tubiphytes/Archaeolithoporella bound-

stone forming large mounds (Fig. 19). Due to dolomitization

and outcrop conditions the shape, size and internal structure of

these mounds are unknown.

According to Flugel (1980, 1981) the bedded platform facies

is composed of bioclastic wackestone (36%), bioclastic

packstone and grainstone (46%), bindstone (10%), grain-

stone/bindstone (3%) and mudstone (2%). The bedded lime-

stones are characterized by a significantly higher taxonomic

diversity compared to the massive mound facies. More than 80

species including fusulinids, corals, brachiopods, gastropods,

pelecypods, echinoderms, calcareous algae, smaller foramini-

fers, trilobites and ammonoids are reported from the bedded

limestones facies.

The massive mound facies contains about 25 species of

smaller foraminifers, fusulinids, calcisponges, bryozoans,

brachiopods, gastropods, pelecypods, echinoderms and ostra-

cods. Bryozoans and echinoderms are the most abundant

invertebrates of the mound facies, from which Flugel (1980,

1981) described three microfacies types:

� b
iopelsparite with varying amounts of Tubiphytes and
Archaeolithoporella;

� in
trabiosparite with fragments of Archaeolithoporella and
angular pelsparitic intraclasts;

� r
eddish biomicrite containing abundant bryozoans, Tubi-
phytes and rare Archaeolithoporella.

The dominant mound-forming organisms are the proble-

matic algae Tubiphytes obscurus Maslov, Tubiphytes car-

inthiacus Flugel and Archaeolithoporella hidensis Endo. Other

taxa include bryozoans, encrusting foraminifers and phylloid

algae, which in combination with eogenetic carbonate cements

formed diagenetic/organic buildups.

Microfacies (a) and (b) are interpreted as Tubiphytes/

Archaeolithoporella boundstones, whereas microfacies (c)

indicates accumulation in quiet water of a somewhat deeper

or protected environment.

According to Flugel (1980, 1981) the Trogkofel mounds

represent ‘‘stratigraphic reefs’’ which probably formed in a

downslope shelf-edge position adjacent to a shallow-water

carbonate platform environment represented by the bedded

limestone facies.

6. Summary and discussion

The small auloporid mounds in the lowermost part of the

Meledis Formation are formed of erect growing auloporid

corals, which reached a maximum height of 5 cm. Very rare

sessile foraminifers are the only binding organisms. Small size

and skeletal volume as well as the scarcity of binding organisms

prevented the formation of a framework structure. The main

function of the auloporid corals was baffling and trapping fine

sediment (Flugel and Krainer, 1992). The auloporid coral

mounds of the Carnic Alps differ significantly from other

auloporid mounds described in the literature (see Watkins,

1959; Stasinska, 1974; Adams, 1984; Eichmuller, 1985;

Scrutton, 1990).

Following the guild concept, which was established by Root

(1967) and adapted for fossil reefs by Fagerstrom (1987, 1988,

1991), organisms found in the algal mounds are members of

different guilds. Each community guild is characterized by a

group of species (‘‘functional group’’) that exploit the same

class of environmental resources in a similar way (Root, 1967).

Fig. 13. Anthracoporella mound (mound II), Lower Pseudoschwagerina Limestone, Schulterkofel. Note the short distance between the two mounds, the sharp

boundary between the massive mound and thin-bedded intermound facies and the downlap of the intermound facies indicating a positive relief of the mound up to 2 m.

Numbers refer to sample number and position of the samples. The position of the mound within the section is shown on Fig. 12.

Fig. 13. Monticule bioconstruit a Anthracoporella (monticule II), Calcaire a Pseudoschwagerina inferieur, Schulterkofel. Noter la courte distance separant les deux

monticules, la limite tranchee entre le monticule massif et les facies finement lites occupant l’espace intermediaire, ainsi que leurs biseaux qui indiquent une

topographie positive du monticule pouvant atteindre 2 m. Les numeros sont ceux des echantillons et correspondent a leur position. La localisation du monticule a

l’interieur de la section est indiquee sur la Fig. 12.


The baffler guild in this study is represented by the calcareous

algae Anthracoporella spectabilis, Archaeolithophyllum mis-

souriense, the binder guild by Archaeolithophyllum missour-

iense, Archaeolithophyllum lamellosum, Ungdarella,

Efluegelia, Tubiphytes, cyanobacteria, sessile foraminifers

Fig. 14. Mound II of the lower part of the Lower Pseudoschwagerina Limestone at S

thin-bedded intermound facies (see also Fig. 13).

Fig. 14. Monticule II de la partie inferieure du Calcaire inferieur a Pseudoschwagerin

bancs intercalaires finement stratifies (voir aussi Fig. 13).

and rarely bryozoans. The destroyer guild includes boring,

rasping and biting organisms such as boring algae, gastropods,

echinoids, and fishes. Members of the dweller guild such as

foraminifers, some fishes, brachiopods, bivalves and solitary

corals neither built nor destroyed the mound framework.

chulterkofel. Note the sharp boundary between the massive mound facies and the

a a Schulterkofel. Noter la limite nette entre le facies massif du monticule et les

Fig. 15. Thin-bedded intermound facies (mostly phylloid algal wackestones and bioclastic wackestones) between two massive algal mounds in the lower part of the

Lower Pseudoschwagerina Limestone at Schulterkofel. The distance between the two mounds is approximately 2 m, the intermound facies which laps on the mound

facies, indicates a positive relief of the mounds.

Fig. 15. Facies intercalaires en petits bancs (principalement des wackestones a algues phylloıdes et des wackestones bioclastiques) separant deux monticules algaires

massifs dans la partie inferieure du Calcaire inferieur a Pseudoschwagerina a Schulterkofel. La distance entre les deux monticules est d’environ 2 m, les facies

intercalaires qui se biseautent sur les monticules sont la preuve du relief positif de ceux-ci au moment du depot.

Fig. 16. Anthracoporella bafflestone/boundstone from Mound I of the Lower Pseudoschwagerina Limestone at Schulterkofel. Large, mostly unbroken, densely

packed thalli of A. spectabilis, rarely encrusted by Tubiphytes/Shamovella form a framework-like structure. Matrix is peloidal lime mud, pore space is filled with

calcite cement (thin section photograph, sample M I/17, width of photograph 17 mm).

Fig. 16. Bafflestone/boundstone a Anthracoporella du Monticule I dans le Calcaire inferieur a Pseudoschwagerina. De grands thalles, serres et generalement intacts,

d’A. spectabilis, quelquefois encroutes par Tubiphytes/Shamovella, forment une sorte de charpente. La matrice est une boue calcaire peloıdale ; les pores de la roche

sont remplis de ciment calcitique (photographie d’une lame mince, echantillon M I/17, largeur de la photographie : 17 mm).


Fig. 17. Thin section photograph of a bioclastic wackestone composed of algal fragments (mostly Anthracoporella spectabilis and phylloid algae, rarely

Epimastopora), echinoderms, diverse shell fragments, smaller foraminifers, Tubiphytes/Shamovella and calcisponges, embedded in peloidal micrite and cemented by

calcite (Mound I, sample M I/21, width of photograph 18 mm).

Fig. 17. Photographie d’une lame mince de wackestone bioclastique compose de debris algaires (surtout des Anthracoporella spectabilis et des algues phylloıdes, plus

rarement des Epimastopora), d’echinodermes, de divers fragments de coquilles, de petits foraminiferes, de Tubiphytes/Shamovella et de calcisponges, emballes dans

une micrite pelloıdale cimentee par de la calcite (Monticule I, echantillon M I/21, largeur de la photographie : 18 mm).


In reefs, there is some overlap between constructor and

baffler guilds, particularly concerning functional morphology.

But concerning skeletonization and skeletal size these two

guilds differ significantly. Members of the constructor guild are

well skeletonized and either colonial or gregarious. The

primary role is to construct the strong, rigid, well skeletonized,

wave- and current-resistant reef framework. Members of the

baffler guild are poorly skeletonized or even non-skeletonized,

many are non-colonial. Their primary role is to baffle currents

while alive (see Fagerstrom, 1987). In contrast to reefs

members of the constructor guild are lacking in the algal

mounds.

Samankassou (1998) stated that Anthracoporella was not

acting as a baffler and that the algal mounds of the Carnic Alps

should be classified as ‘‘skeletal framework mounds’’. But

Anthracoporella, which is a well skeletonized alga that grew

upward as cylindrical to subcylindrical solitary branching

tubes to heights of several centimetres, was not able to

construct a wave- and current-resistant framework. Organisms

constructing a framework are restricted to reefs and are not

found in mounds (see Fagerstrom, 1987). Although the upright

growing thalli of Anthracoporella could not have provided a

substantial ‘‘reef framework’’ and could not have withstood

current and wave turbulence (see Krainer, 1995), and although

baffling of fine sediment seems to have been quite inefficient,

the main function of Anthracoporella was baffling currents.

Only in densely packed associations with a framework-like

structure, locally observed in the mounds of the Lower

Pseudoschwagerina Limestone, Anthracoporella may have

also functioned as a constructor. Fagerstrom (1987) pointed out

that in situ algal bafflestones are rare because the delicate algal

thalli were easily broken by wave and current action, but

nonetheless Anthracoporella acted as a baffler, thus being a

member of the baffler guild and not of the constructor guild. In

contrast to the statement of Samankassou (1998), toppled and

even transported algal thalli are frequently found within the

mound facies indicating that during mound growth stronger

currents periodically occurred. Most of the internal micrite

within the mound facies was formed in situ by the decay of

algal thalli, especially by benthic microbial communities

trapping and binding detrital sediment and/or producing

micritic and micropeloidal sediment (‘‘automicrite’’). Only a

small amount of fine-grained sediment was accumulated by

baffling.

In the algal mounds at Schulterkofel, members of the binder

guild were responsible for the formation of a positive relief by

binding together and stabilizing the algal thalli, forming a

framework-like structure. Locally inorganic ‘‘framework

cement’’ also contributed to the stabilization of the mounds,

particularly in densely packed associations where pore space

was not filled with micrite.

Although mounds of the Auernig Formation and Lower

Pseudoschwagerina Limestone (see Auernig and Schulterkofel

mounds below) are both formed mainly of Anthracoporella

spectabilis, there are some significant differences:

� A
uernig mounds form biostromes; Schulterkofel mounds
both, biostromes and bioherms;

Fig. 18. The steep northern wall of the Trogkofel (2280 m) composed of

bedded Trogkofel Limestone in the lower part, overlain by massive Trogkofel

Limestone representing Tubiphytes (Shamovella)/Archaeolithoporella-mounds.

The wall is approximately 300 m high.

Fig. 18. La paroi nord escarpee du Trogkofel (2280 m), composee du calcaire

stratifie de Trogkofel a la partie inferieure, surmonte par le calcaire massif de

Trogkofel avec ses bioconstructions a Tubiphytes (Shamovella)/Archaeolitho-

porella. L’escarpement a une hauteur d’environ 300 m.


� in
the Auernig mounds, the transition from the intermound
facies to the mound facies is gradational; in the Schulterkofel

mounds there is a sharp boundary between the two facies;

� A
uernig mounds had almost no positive relief (biostromes),
whereas the Schulterkofel mounds (bioherms) formed a

positive relief up to 2 m;

� A
uernig mounds lack zonation; the Schulterkofel mounds
have poor zonation with the occurrence of calcisponges at the

base and top of some biohermal mounds;

� th
e dominant mound-building organism in both mound types
is Anthracoporella. In the Auernig mounds Archaeolitho-

phyllum missouriense is a subordinate component and in the

Schulterkofel mounds some calcisponges and phylloid algae

are present;

� in
the Auernig mounds cement is lacking. In the Schulterko-
fel mounds there is substantial ‘‘framework cement’’ in

densely packed algal associations; rare brecciation is also

observed;

� th
e Schulterkofel mounds occur within a transgressive
sequence; the Auernig mounds formed during relative sea

level highstands. All algal mounds are under- and overlain by

thin-bedded, fossiliferous limestones of the intermound

facies, which is characterized by a significantly higher

taxonomic diversity compared to the mound facies.

Upper Carboniferous–Lower Permian algal mounds are

particularly well studied in the Holder and Laborcita

Formations of the Sacramento Mountains, New Mexico (e.g.

Wilson, 1967; Toomey et al., 1977; Mazullo and Cys, 1979;

Bowsher, 1986). These mound complexes occur in a similar

stratigraphic setting as the Auernig and Schulterkofel mounds,

but differ in many respects:

The Yucca Mound Complex of the Holder Formation

(Virgilian) is a phylloid algal organic buildup, which is

dominantly composed of Ivanovia and subordinately of

Macroporella. Yucca mound is characterized by a well defined

zonation reflecting three growth stages: (a) foundational phase

represented by a basal bioclastic wackestone pile; (b)

constructional framework phase (‘‘skeletal mound stage’’)

composed of a micritic bafflestone core rich in phylloid algae,

and (c) a climax boundstone phase (‘‘crestal boundstone’’). In

situ brecciation is common, particularly in the phylloid algal

facies of the constructional framework phase. The mound

complex was interrupted several times by drops of sea level.

The phylloid algal facies of phase (b) accumulated during

constant sea level; the boundstone facies of phase (c) during

regression (see Wilson, 1975; Toomey et al., 1977; Bowsher,

1986).

The primary mound-building organisms of the Scorpion

Mound Complex of the Laborcita Formation (Lower Wolf-

campian) are stromatolitic algae (microbial micrite) and

phylloid algae related to the genus Anchicodium. The mound

complex shows a slight vertical biotic zonation, which is related

to progradation during drop of sea level. The phylloid algal

mound facies is characterized by extreme in situ brecciation

and complex diagenetic history (see Cys and Mazullo, 1977;

Mazullo and Cys, 1979; Shinn et al., 1983; Bowsher, 1986).

In contrast to the Auernig and Schulterkofel mounds many

Late Paleozoic phylloid algal mounds were characterized by

high primary porosities, resulting in complex diagenetic history

and intensive in situ brecciation (Toomey and Winland, 1973;

Cys and Mazullo, 1977; Mazullo and Cys, 1979; Choquette,

1983; Shinn et al., 1983; Roylance, 1990).

Late Paleozoic mounds commonly were subaerially exposed

resulting in vadose diagenetic processes and the formation of

secondary porosities (e.g. Wilson, 1967, 1975; Toomey et al.,

1977; Mazullo and Cys, 1979; Choquette, 1983; Heckel, 1983;

Shinn et al., 1983; Dawson and Carozzi, 1986; Roylance,

1990).

Many phylloid algal mounds (including Yucca and Scorpion

mounds) occur within a regressive phase and are overlain by

high-energy deposits forming the ‘‘capping beds’’ sensu Wilson

(1975).

The Carnic Alps are one of the few places where the

dasycladacean alga Anthracoporella is the dominant mound-

building organism. There, Anthracoporella mounds occur in

the Auernig Group (Krainer, 1995) and in the Lower

Fig. 19. Tubiphytes (Shamovella)/Archaeolithoporella boundstone from the mound facies of the Trogkofel Limestone at Trogkofel. Pencil for scale.

Fig. 19. Boundstone a Tubiphytes (Shamovella)/Archaeolithoporella d’un facies bioconstruit du calcaire de Trogkofel a Trogkofel. Le crayon donne l’echelle.


Pseudoschwagerina Limestone (Rattendorf Group). Recently

Minwegen (2001) described Anthracoporella mounds from the

Kasimovian of the Cantabrian Mountains in Spain.

Compared to the Late Paleozoic phylloid algal mounds

(particularly to the well studied Yucca and Scorpion mounds),

the algal mounds of the Carnic Alps differ in the following

points:

� m
ound building organisms: in the Late Paleozoic algal
mounds of the Carnic Alps the dasycladacean alga

Anthracoporella spectabilis is the dominant mound-building

organism. Of minor importance are Archaeolithophyllum

missouriense, Tubiphytes, smaller foraminifers and calcis-

ponges;

� s
tructure: in outcrop the mounds are composed of massive,
homogenous grey limestone, characterized by clusters of

Anthracoporella (forming small ‘‘algal bushes’’) with space

between filled with micritic sediment;

� z
onation: in contrast to many Late Paleozoic mounds the algal
mounds of the Carnic Alps are poorly to non-zoned (phylloid

algae and calcisponges occur at the base and on top);

� p
reservation: the mound facies is well-preserved. Due to the
low primary porosity, in situ brecciation is very rare and the

amount of cement low;

� a
lgal mounds of the Carnic Alps formed during a
transgressive phase or during relative sea level highstands

and were not subject to subaerial exposure. Thus, they lack

vadose diagenetic processes, secondary porosities and

brecciation.

In limestones of the Auernig Group and Rattendorf Group,

calcareous algae, particularly Anthracoporella spectabilis, are

by far the most abundant biogenic component. During optimum

growth conditions the sea bottom was colonized by carbonate-

producing organisms, mainly by calcareous algae. Due to its

high reproduction rate, Anthracoporella spectabilis grew in

such profusion that almost all other organisms except some

epiphytic forms (encrusting foraminifers, Tubiphytes, encrust-

ing algae) were excluded. Therefore, the taxonomic diversity of

the mound facies is much lower than that of the intermound

facies.

It is surprising that phylloid algae, although abundant in the

intermound facies of the Lower Pseudoschwagerina Limestone

and forming many Late Paleozoic mounds, particularly in

North America, did not build mounds in the Carnic Alps.

The differences between the Anthracoporella mounds of the

Auernig Formation and Lower Pseudoschwagerina Limestone

appear to be caused by different growth densities. In the

Schulterkofel mounds Anthracoporella seems to have grown in

denser associations and were rapidly stabilized by binding

organisms resulting in a framework-like structure with some

open pore space which was filled by eogenetic cement,

resulting in the formation of biohermal mounds with a positive

structure and sharp boundaries between mound and intermound

facies.

The Trogkofel mounds are formed of diagenetic/organic

boundstones composed of the binding organisms Tubiphytes

and Archaeolithoporella, and of eogenetic cements. According

to Flugel (1981) many criteria of the Trogkofel mounds are

similar to those of the Permian Capitan Reef Complex of the

Guadalupe Mountains in southern New Mexico - West Texas.

Recent investigations by Fagerstrom and Weidlich (1999,

2005) and Weidlich and Fagerstrom (1998, 1999, 2001)

indicate that, in contrast to the boundstone facies of the


Trogkofel mounds, the upper Capitan Massive of the Capitan

Reef Complex is a biological reef displaying three growth

stages controlled by sea level changes. Stage 1 of the Capitan

Reef Complex is composed of a skeletal framework built by the

upward growth and accretion of erect sponges, stabilized by

Archaeolithoporella hidensis, Tubiphytes and syndepositional

‘‘framework cement’’. This facies is not known from the

Trogkofel Limestone. The low-growing organisms Tubiphytes

and Archaeolithoporella, and marine-phreatic cement are only

dominant in the micro-framework of the Gigantospongia-zone

and in the last growth stage, the ‘‘Tubiphytes reef stage’’. The

Trogkofel mounds are similar to the ‘‘Tubiphytes thickets’’ of

stage 2 which contain a very impoverished fauna suggesting

much shallower water and higher environmental stress (‘‘low-

growing community’’ composed of Shamovella obscura,

Archaeolithoporella hidensis, microbial micrite and some

bryozoan fragments).

Some similarities also exist to the impoverished level-

bottom community of Shamovella, Archaeolithoporella, sessile

foraminifers and microbes of stage 3 described by Weidlich and

Fagerstrom (1999), which in contrast to the large Tubiphytes/

Archaeolithoporella mounds of the Trogkofel Limestone

formed small isolated ‘‘Tubiphytes patches’’ on outer shelf

grainstone intervals.

Acknowledgments

I am very grateful to Al Fagerstrom (Ann Arbor, USA) for

helpful suggestions and for improving the English. I would also

like to thank Erik Flugel (Erlangen, Germany), Daniel Vachard

(Villeneuve d’Ascq, France) and an anonymous reviewer for

carefully reviewing an early version of the manuscript and

making useful comments. I thank Daniel Vachard (Villeneuve

d’Ascq, France) for translating the French text.

This paper is dedicated to Erik Flugel.

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Late Paleozoic reef mounds of the Carnic Alps (Austria/Italy)