Palaeogeography, Palaeoclimatology, Palaeoecology 201 (2003) 89^111
www.elsevier.com/locate/palaeo
Provenance analysis of Oligocene autochthonous and
allochthonous coralline algae: a quantitative approach
towards reconstructing transported assemblages
Michael W. Rasser a; , James H. Nebelsick b
a
Institute of Geology and Palaeontology, University of Graz, Heinrichstrasse 26, 8010 Graz, Austria
b
Institute of Geosciences, University of Tu«bingen, Sigwartstrasse 10, 72076 Tu«bingen, Germany
Received 6 March 2002; accepted 20 June 2003
Abstract
The Oligocene shallow-water carbonates of the Lower Inn Valley (Tyrol, Northern Calcareous Alps) contain a
rich coralline algal flora. These carbonates are known from two distinct settings: (1) autochthonous limestones and
(2) debris flows intercalated with deeper water marls. The carbonate facies are dominated not only by crustose
coralline algae (Corallinaceae, Rhodophyta), but also by smaller and larger benthic foraminifers, bryozoans, corals as
well as lithoclasts of Triassic origin. Five species of coralline algae are identified and described in detail: Lithoporella
melobesioides, Lithothamnion sp. A, Lithothamnion sp. B, Mesophyllum sp., and Sporolithon sp. The distribution of
algal taxa shows distinct relationships to non-algal biota and substrates: L. melobesioides preferably encrusts other
coralline algae, Lithothamnion sp. A is found encrusting bryozoans, Lithothamnion sp. B encrusts corals, while
Mesophyllum sp. grows directly on fine-grained, soft substrates. Besides the fact that algal taxa reveal close
relationships to other components, it can also be shown that algal assemblages are highly correlated to carbonate
facies types. Hierarchical cluster analysis based on the relative abundance of taxa reveals five coralline algal
assemblages showing distinct distribution patterns among carbonate facies. While two of the assemblages are
restricted to the debris flows, the other three were found in both debris flows and autochthonous occurrences. A
correlation between algal assemblages and carbonate facies allows the following conclusions to be made: (1) Both
coralline algal taxa in particular and algal assemblages as a whole show distinct relations to water depth (herein
referred to as a summary of light conditions and hydrodynamic energy) and substrate relationships. This makes them
potentially valuable indicators for palaeoecological reconstructions. (2) Most of the coralline algal assemblages in
allochthonous occurrences (i.e. debris flow) can be traced back to facies patterns in autochthonous occurrences. This
indicates that a thorough microfacies analysis combined with a systematic study of specific components can be very
useful in the reconstruction of palaeoenvironments, even if these are not preserved in their original context. (3) Some
of the coralline algal assemblages within debris flows cannot be traced to autochthonous facies and do not seem to
reflect primary facies compositions as they contain an atypical mixture of algal taxa and other components. These are
characterised by a relatively high abundance of lithoclasts (usually s 20% of the components) and a high degree of
fragmentation of coralline algae thalli.
8 2003 Elsevier B.V. All rights reserved.
* Corresponding author. Tel.: +43-316-380-8732; Fax: +43-316-380-9871.
E-mail addresses: [email protected] (M.W. Rasser), [email protected] (J.H. Nebelsick).
0031-0182 / 03 / $ ^ see front matter 8 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0031-0182(03)00512-1
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Keywords: Oligocene; coralline algae (Corallinaceae, Rhodophyta); coralline algal assemblages; carbonate facies; palaeoecology;
Northern Calcareous Alps
1. Introduction
Coralline algae (Corallinaceae, Rhodophyta)
are important components and carbonate producers in the Cenozoic and are present in a variety of di¡erent carbonate and/or siliciclastic facies. There is, however, surprisingly little
information available concerning their taxonomy
and palaeoecology. The lack of knowledge is especially evident for Oligocene coralline algal assemblages on which there are few studies worldwide (e.g. Manker and Carter, 1987; Vannucci et
al., 1997; Basso et al., 1998; Bassi and Nebelsick,
2000; Nebelsick et al., 2000; Nebelsick and Bassi,
2000; Kaiser et al., 2001). Such studies are, however, essential for eventual palaeobiogeographic
reconstructions or evolutionary scenarios (compare Aguirre et al., 2000a,b).
The coralline algae included in this investigation originate from Lower Oligocene carbonates
of the Lower Inn Valley. These carbonates form
part of a siliciclastic-dominated sedimentary sequence (‘Lower Inn Valley Tertiary’) along the
southern coastline of the Paratethys, deposited
in a pull-apart^piggyback basin (e.g. Steininger
et al., 1991; Wagreich, 1995; Ro«gl, 1998; Faupl
and Wagreich, 2000; Ortner and Stingl, 2001).
This succession is, in part, highly fossiliferous
and has generated a long history of palaeontological research especially concerning the rich mollusc fauna (e.g. Lo«¥er, 1999; Lo«¥er and Nebelsick, 2001) and foraminiferal assemblages (e.g.
Lu«hr, 1962; Lindenberg, 1965; Scherbacher,
2000; Scherbacher et al., 2001). The stratigraphic
setting and complex tectonic history of these sediments is reviewed in detail by Ortner and Stingl
(2001). Recently, Nebelsick et al. (2001) de¢ned
the carbonate facies patterns of these autochthonous and allochthonous (i.e. debris £ows) carbonates.
This study is based on the question whether or
not the distribution of coralline algal taxa re£ects
the facies patterns described by Nebelsick et al.
(2001). They identi¢ed six di¡erent carbonate facies types, all of which contain coralline algae,
from both autochthonous settings and allochthonous debris £ows. All the facies recognised in the
autochthonous carbonates are also present reworked in the debris £ows. A single facies, composed of bioclastic packstones, is restricted to the
debris £ows.
The main topics of this paper are: (1) a documentation of crustose coralline algae, (2) the definition of coralline algal assemblages based on
hierarchical cluster analysis, (3) to investigate
the relationships between coralline algal assemblages and carbonate facies as a whole, and between coralline algal taxa and non-algal biota in
particular, (4) to study the palaeoecological factors in£uencing the particular algal taxa, and
(5) to analyse the potential of coralline algal assemblages in debris £ows for the recognition and
reconstruction of unpreserved palaeoenvironments. After a brief summary of the carbonate
facies distinguished by Nebelsick et al. (2001),
we give a systematic description of coralline algae,
including an identi¢cation key. An open nomenclature is used due to the large uncertainties concerning coralline algal taxonomy. Detailed anatomical descriptions are provided in order to
allow comparisons to other algal £oras. The distribution, substrate relationships, and associated
biota are described for each species. After a description of the coralline algal distribution among
carbonate facies, we de¢ne coralline algal assemblages as revealed by hierarchical cluster analysis.
The discussion focusses on palaeoecological factors in£uencing coralline algal distribution and
the possibility of reconstructing non-preserved facies patterns using this algal group.
2. Study area, material, and methods
The coralline algae presented here are found
within the Werlberg Member of the Paisslberg
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Formation (Early Oligocene), which is described
in detail in Nebelsick et al. (2001) and Ortner and
Stingl (2001). Samples were taken from the Bergpeterl Quarry and its surrounding area as well as
º sterndorf and Kufsteiner Wald localfrom the O
ities (Fig. 1A). The studied sections in the Bergpeterl Quarry and vicinity (Fig. 1B) include the
Bridge section, the Bergpeterl Quarry-B as well
as the Bergpeterl Quarry-SW (the type locality
of the Werlberg Member). Autochthonous occurrences are found in the Bergpeterl Quarry-SW
º sterndorf and
section and the isolated localities O
Kufsteiner Wald. Debris £ows representing allochthonous occurrences within the ‘Zementmergel’ marls are present in the Bridge section and
the Bergpeterl Quarry-B section.
Thin sections used for coralline algal identi¢cation (5U5 cm and 8U10 cm) were cut perpendicular to bedding planes. Measurements of coralline
algal thalli were made at a magni¢cation of 400U
to the nearest 1 Wm. The cell diameters of peripheral ¢laments were measured in sections perpendicular to the direction of ¢lament growth. All
91
other dimensions were measured in sections parallel to growth direction. At least 20 cells of each
cell type were measured, if possible. Mean (M)
and standard deviation (SD) were calculated.
Cells of core ¢laments were measured near the
dorsal surface to avoid ¢lament branching zones,
which are di⁄cult to recognise in thin sections.
Cells of peripheral ¢laments were measured in
central thallus parts only, as most outer cell layers
show micritisation. All samples are stored at the
Institute of Geosciences, University of Tu«bingen,
Germany.
The quanti¢cation of carbonate components
and coralline algal taxa, given in Table 1, was
conducted using estimation charts as described
by Flu«gel (1982), who showed that the estimation error is negligible compared to point counting and with relation to the sampling error. A
Q-mode, hierarchical cluster analysis was conducted using the SPSS program package (Bu«hl
and Zo«fel, 1996) on these data, in the same
way as recently conducted by Rasser (2000)
and Nebelsick et al. (2001). A preliminary cluster
Fig. 1. (A) Study area in the Lower Inn Valley, Tyrol, Austria. Studied localities are (1) Bergpeterl Quarry with the autochthonous occurrence Bergpeterl Quarry-SW and the allochthonous occurrences Bergpeterl Quarry B and Bridge section (not separated
º sterndorf (OD) and (3) Kufsteiner Wald (KW). (B) Details of the
in the ¢gure), as well as the autochthonous occurrences (2) O
Bergpeterl Quarry sections.
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Table 1
Algal assemblages revealed from cluster analysis (Fig. 6), sample numbers, carbonate facies and component distribution of the
particular samples, and relative abundance of coralline algal species in the samples
‘Autocht.’ indicates whether the sample is part of an autochthonous occurrence; ca, coralline algal facies; cc, coral^coralline algal
facies; cb, coralline algal^bryozoan facies; b, bryozoan facies; f, foraminiferal facies; L. A, Lithothamnion sp. A; L. B., Lithothamnion sp. B; M., Mesophyllum sp.; S., Sporolithon sp.; Det., algal detritus.
analysis using the nearest-neighbour method
was calculated to eliminate outliers. The ¢nal
cluster analysis was conducted using Ward’s
clustering method with a Euclidean distance measurement. The percentage data were transformed
with the arcsin of the square root of each value.
3. Results
3.1. Stratigraphy and sedimentary setting
Palaeogene sediments of the Lower Inn Valley
represent transgressive sediments sealing a deeply
eroded Triassic basement (Krois, 1992; Nebelsick
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et al., 2001; Ortner and Stingl, 2001). The studied
sediments are part of the Lower Oligocene
(NP22; Lo«¥er, 1999) Paisslberg Formation
(Figs. 1, 4 and 5) dominated by ca. 200 m of
steeply dipping, ¢nely laminated, basinal marls
(‘Zementmergel’), which become ¢ner towards
the top. Shallow water carbonate sediments within the Paisslberg Fm. are contained within the
Werlberg Member (Ortner and Stingl, 2001).
Carbonates of the Werlberg Mb. occur in two
distinct sedimentary settings: (1) Autochthonous
carbonates transgressing over Triassic carbonates.
They can change to basinal marls up-section and
are also known from isolated horsts surrounding
the basin. (2) Numerous allochthonous debris
£ows occur within the ‘Zementmergel’ marls
(Fig. 5). These occur as isolated as well as
bundled debris £ows and are described in detail
in Nebelsick et al. (2001). The most massive occurrence is found in the 8 m long Bridge section
and consists of a stack of distinct debris £ows
which can reach more than 1 m in thickness and
contain decimetre-sized, heavily bio-eroded, Triassic clasts. Debris £ows within the Bergpeterl-B
section include isolated bioclastic limestone beds
up to 80 cm thick as well as bundled debris £ows,
ranging up to 50 cm in thickness.
The Early Oligocene was a time of synsedimentary faulting in the Lower Inn Valley, leading to
the formation of uplifted Triassic fault blocks
with (half-)graben geometry. This caused subsidence and deposition of basinal marls, on the
one hand, and deposition of autochthonous shallow water carbonates on top of fault blocks, on
the other. Synsedimentary faulting is also seen as
the driving force for the formation of the abovementioned debris £ows, which transported material from the topographic highs into the basin
(Ortner and Stingl, 2001).
3.2. Carbonate facies
The studied carbonates consist of rudstones
and packstones dominated by coralline algae,
larger and smaller benthic foraminifers, corals,
bryozoans and lithoclasts (Fig. 2). Mollusks, echinoderms, brachiopods and serpulids are subordinate. Six carbonate facies were distinguished
93
based on component distribution, fabric analysis,
and statistical treatment (Q-mode, hierarchical
cluster analysis, partial correlation, R-mode principal-components analysis) of semi-quantitative
data of biogenic components (Nebelsick et al.,
2001):
(1) The coralline algal facies which consists of
£oat- to rudstones with a pack- to wackestone
matrix is dominated by coralline algae followed
by bryozoans and small foraminifers (Fig. 2B).
(2) The coral^coralline algal facies shows rudstones with wacke- to packstone matrix and are
dominated by corals closely followed by coralline
algae; lithoclasts can also be common (Fig.
2C,D).
(3) The coralline algal^bryozoan facies with
£oat- to rudstones with packstone matrix are
dominated by both coralline algae and bryozoans; large and small benthic foraminifers are
common (Fig. 2E,F).
(4) The bryozoan facies consists of £oat- to
rudstones with pack- to wackestone matrix and
is totally dominated by bryozoans accompanied
by larger foraminifera. Coralline algae are
under-represented (Fig. 2G).
(5) The foraminiferal facies consisting of £oatto rudstones with pack- to wackestone matrix is
dominated by both large and small benthic foraminifera. Coralline algae and bryozoans are also
common along with lithoclasts (Fig. 2H).
(6) Finally, the bioclastic packstone facies consists of relatively well-sorted packstones containing poorly rounded and highly fragmented bioclasts including small fragments of unidenti¢ed
coralline algae.
The ¢rst ¢ve facies are found in both autochthonous and allochthonous settings, while the bioclastic packstone facies is restricted to allochthonous settings. The interpreted facies patterns
(Nebelsick et al., 2001) show both lateral changes
within shallow water and along a depth gradient:
(1) in near-shore environments a lateral transition
from the coral^coralline algal facies to the coralline algal facies and the foraminiferal facies and
(2) from shallow to relatively deeper water from
the coralline algal through the coralline algal^
bryozoan facies to the bryozoan facies. Basinal
sediments are formed by the ‘Zementmergel’
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marls. Both trends incorporate a shift from coarse
to ¢ne sediments and from more turbulent to quieter water conditions.
3.3. Systematics of coralline algae
3.3.1. Description
The terminology for taxonomic features follows
Woelkerling (1988) and Rasser and Piller (1999),
the identi¢cation of genera is in accordance with
Braga et al. (1993) and Rasser and Piller (1999).
The designation of fossil species su¡ers from the
fact that the vast majority of species are poorly
described and type specimens are partially missing. There are also few modern taxonomic revisions following neophytical concepts of species
di¡erentiation. Although there have been several
e¡orts to revise and re-describe original material
(e.g. Moussavian and Kuss, 1990; Piller, 1994;
Rasser and Piller, 1994; Braga and Aguirre,
1995; Aguirre et al., 1996; Basso et al., 1997;
Aguirre and Braga, 1998; Bassi et al., 2000),
most fossil species cannot be identi¢ed with con¢dence. An open nomenclature is used for this
reason, as suggested by Bassi (1998) and Rasser
and Piller (1999). The latter authors also discuss
the identi¢cation of genera found in the current
study. A detailed description is not given for Lithoporella melobesioides, because it is one of the
few species with a clear taxonomic status. Instead,
a list of synonymies for the most important descriptions is given. Terminology concerning coralline algal growth forms is used following that of
Woelkerling et al. (1993).
In addition to the coralline algae, only one
fragmented specimen of Polystrata alba (Pfender)
95
Denizot was found. This alga belongs to the Family Peyssonneliaceae Denizot and di¡ers from coralline algae by its aragonitic cell walls. A systematic and anatomic review on this species was given
by Bassi (1997).
Division Rhodophyta Wettstein, 1901
Class Rhodophyceae Rabenhorst, 1863
Order Corallinales Silva and Johansen, 1986
Family Corallinaceae Lamouroux, 1812
Subfamily Mastophoroideae Setchell, 1943
Lithoporella melobesioides (Foslie) Foslie, 1909
1909 Lithoporella melobesioides (Foslie) Foslie, p. 59.
1957 Lithoporella melobesioides Johnson, p. 234, pl. 37,
¢g. 5; pl. 43, ¢gs. 1, 2; pl. 49, ¢g. 4.
1982 Lithoporella melobesioides Turner and Woelkerling,
pp. 218 ¡., ¢gs. 2, 4, 6, 7^11, 15^17, 20, 21, 25, 26.
Lithoporella melobesioides is well known in fossil material and can be easily identi¢ed by its unistratose thallus with large cells. Only encrusting
growth forms were found.
Occurrence : L. melobesioides accounts for only
1% of the total algae and ranges from 0 to 5% in
the particular samples. This species is restricted to
the coral^coralline algal facies in which it contributes only 3% of the total algal £ora. It is found
encrusting other, unidenti¢ed algal thalli.
Subfamily Melobesioideae Bizzozero, 1885
Lithothamnion sp. A (Fig. 3A,B)
Description : Growth form encrusting to lumpy
and fruticose. Core ¢laments are non-coaxial pre-
Fig. 2. Carbonate microfacies. (A) Lithothamnion sp. encrusting a celleporid cheilostome bryozoan; the coralline algae show
º sterndorf, thin section: UIT7, image width: 14.40 mm. (B) Coralline algal facies; rudstone
prominent protuberances; locality: O
with packstone matrix; coralline algae encrusting a bryozoan in the upper left corner, a number of calcite veins cut through the
section; locality: Bergpeterl Quarry-SW, thin section: IT4, image width: 14.00 mm. (C) Coral^coralline algal facies. Rudstone
with packstone matrix; complex encrustation sequence in the lower right with a coral encrusted by bryozoan encrusted by coralline algae; locality: Bergpeterl Quarry-B, thin section: IT26C, image width: 15.13 mm. (D) Coral^coralline algal facies. Section
showing fragmented corals encrusted by thin algal crusts; locality Bergpeterl Quarry-B, thin section: UIT26, image width: 15.32
mm. (E) Coralline algal^bryozoan facies; rudstone with packstone matrix; locality: Bergpeterl Quarry-SW, thin section: IT6, image width: 10.64 mm. (F) Coralline algal^bryozoan facies; rudstone with packstone matrix with a bilaminar, cheilostome bryozoan to the upper right; locality: Bergpeterl Quarry-SW, thin section: IT6, image width: 5.82 mm. (G) Bryozoan facies, packstone
with most components parallel to bedding; locality: Bergpeterl Quarry-SW, thin section IT9, image width: 18.26 mm. (H) Foraminiferal facies showing packstone fabric; locality: Bergpeterl Quarry-B, thin section: IT25, image width: 9.75 mm.
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dominantly curve outward, cell fusions are
present. The core portion is 50^100 Wm thick ;
the cell length is 14^22 Wm (M = 18, SD = 4), the
diameter 7^11 Wm (M = 9, SD = 1). Peripheral ¢laments show 170^200 Wm thick growth rhythms;
cell shape irregular, cell fusions are present; the
cell length is 7^28 Wm, (M = 16, SD = 6), the diameter 8^13 Wm (M = 10, SD = 1). Subepithallial
initials and epithallial cells are not preserved.
The tetrasporangial conceptacles are multiporate; old conceptacles are buried within the thallus. A cavity is formed between the conceptacle
roof and overgrowing thallus portions. The diameter of tetrasporangial conceptacles is 200^
750 Wm, the height 150^200 Wm. The roof thickness is 45^72 Wm. Length of cells in the roof 11^
20 Wm (M = 14, SD = 3), diameter 5^9 Wm (M = 7,
SD = 2). Conceptacles are either completely raised
above or are slightly sunken below the thallus
surface.
Occurrence: Lithothamnion sp. A accounts for
27% of the algae in all samples. It contributes 0^
61% of the algae within speci¢c samples. This
species is most typically associated with bryozoans and is the only algal species that was found to
encrust bryozoans, beside one specimen of Mesophyllum sp. It is abundant in all facies and is the
most common taxon besides Lithothamnion sp. B.
It is, however, absent in the autochthonous occurº sterndorf and Kufsteiner Wald.
rences of O
In the coralline algal facies, where Lithothamnion sp. A accounts for 9^61% of the algae, it
predominantly forms fragile, isolated crusts or
branches and can encrust bryozoans. In this facies
it additionally forms crusts and fruticose branches
that are frequently fragmented.
In the bryozoan facies, where algae only ac-
97
count for 8% of the components, it represents
half of the algae and is only associated with
Mesophyllum sp. In this facies it is only present
as fragmented, isolated, fruticose branches.
Lithothamnion sp. B (Fig. 3C^E)
Description : Growth form encrusting to lumpy.
Core ¢laments are non-coaxial. The core portion
is 90^130 Wm thick and is restricted to the ventral
thallus portion; ¢laments curve both dorsally and
ventrally. The cell length is 16^25 Wm (M = 21,
SD = 3), the cell diameter 9^13 Wm (M = 10,
SD = 1). Cell fusions are present. Peripheral
¢laments are restricted to the dorsal thallus portion. Growth rhythms and trichocytes are absent.
The cell length is 5^11 Wm (M = 10, SD = 2), the
cell diameter 9^11 Wm (M = 10, SD = 1). Subepithallial initials and epithallial cells are not preserved.
The tetrasporangial conceptacles are multiporate and old conceptacles are buried within the
thallus, in which case, a cement-¢lled cavity is
formed above the conceptacle pores. Most conceptacles are situated close to the core portion
and are then usually separated from it by only
one peripheral cell layer. The conceptacle £oor
is situated slightly below the thallus surface. The
conceptacle height is 90^160 Wm (M = 138,
SD = 12), the conceptacle diameter 190^410 Wm
(M = 321, SD = 72). Conceptacle roofs are not
rimmed; the roof thickness is 31^49 Wm (usually
ca. 45 Wm). The diameters of conceptacle pores
are not measurable with con¢dence. The cell
length within conceptacle roofs is ca. 5^9 Wm,
the cell diameter ca. 6^8 Wm.
Sexual conceptacles are monoporate, the conceptacle position with respect to the thallus sur-
Fig. 3. Coralline algal taxa. (A) Fruticose branch of Lithothamnion sp. A, showing distinct growth rhythms characteristic for this
species; conceptacles are cut tangentially; sample UIT94/19, image width: 2.64 mm. (B) Lithothamnion sp. A, showing a multiporate conceptacle and cavity between old conceptacle and overgrowing thallus; sample UIT94/19, image width: 1.38 mm. (C) Lithothamnion sp. B, warty or lumpy growth form in axial section; sample UIT94/19, image width: 2.14 mm. (D) Lithothamnion
sp. B, showing a change from encrusting (below) to warty (above) growth form; sample UIT95/6, image width: 1.61 mm.
(E) Close-up of Lithothamnion sp. B, showing multiporate conceptacles; sample UIT94/19, image width: 0.97 mm. (F) Mesophyllum sp., encrusting growth form; sample UIT9420A, image width: 2.78 mm. (G) Detail of panel F, showing coaxial core portion; note that conceptacle is situated close to the core, sample UIT9420A, image width: 1.39 mm. (H) Sporolithon sp., encrusting to slightly warty growth form; sample UIT94/26, image width: 2.72 mm. (I) Detail of panel H, showing tetra/bisporangial
conceptacles arranged in sori and core ¢laments, sample UIT94/26, image width: 1.38 mm.
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face is the same as described for tetrasporangial
conceptacles. The spermatangial initials are not
preserved. The conceptacle diameter is 370^430
Wm, the height 280^250 Wm. The pore length (corresponding to the maximum roof thickness) is
180^190 Wm, the diameter ca. 50 Wm. The conceptacle roof thickness aside the pores is 55^65 Wm;
the cell length in the roof is ca. 9^13 Wm, the
diameter ca. 6^7 Wm.
Occurrence: Lithothamnion sp. B accounts for
30% of the algae in all samples and is therefore
the most abundant species, ranging from 0 to 84%
of the algae. This species is most frequently associated with corals and characteristically encrusts
them, but it is particularly less frequently associated with bryozoans.
This species dominates many samples of the
coral^coralline algal facies. In the autochthonous
part of the coralline algal facies it is characterised
by fragile but unfragmented, encrusting thalli in
most samples. In the allochthonous samples of
this facies it encrusts coral fragments ; fractured
surfaces reveal that corals were encrusted before
fragmentation. Both in the coral^coralline algal
facies and in the coralline algal facies, this species
encrusts other biota, mostly corals; isolated
branches are also known.
The thalli found in the coralline algal^bryozoan
facies are represented by unattached, partly fragmented, isolated branches. In this facies it is particularly less abundant than Lithothamnion sp. A.
Within the foraminiferal facies, Lithothamnion
sp. B is only known from one sample, where it
encrusts unidenti¢ed bioclasts ; they most probably represent unpreserved corals.
It is particularly rare in the bryozoan facies,
where it is only represented by fragmented
branches.
Mesophyllum sp. (Fig. 3F,G)
Description: Growth form encrusting. The core
portion is 130^200 Wm thick, coaxial, and situated
ventrally. Filaments curved to both sides and cell
fusions occur. The cell length is 25^36 Wm
(M = 31, SD = 4), the diameter 9^11 Wm (M = 11,
SD = 1). The peripheral portion is 27^55 Wm
thick ; growth rhythms and trichocytes are absent.
The cell length is 7^9 Wm (M = 8, SD = 1), the
diameter 5^6 Wm (M = 6, SD = 1). Subepithallial
initials and epithallial cells are not preserved.
Tetrasporangial conceptacles are multiporate
and distinctively raised above the thallus surface.
The conceptacle £oors are positioned directly on
the core portion and are sunken ca. 10^50 Wm
below the thallus surface. The conceptacle height
is 170^200 Wm, the diameter 520^640 Wm. The
roof thickness is 60^75 Wm, but the pores are
not measurable. The cell length in the roof is ca.
9 Wm, the diameter ca. 6 Wm. Carposporangial
and sexual conceptacles are unknown.
Occurrence : Mesophyllum sp. accounts for 27%
of the algae in all samples and thus shows the
same total abundance as Lithothamnion sp. A,
ranging from 0 to 59% of the algae within speci¢c
samples. This species usually did not encrust hard
substrate, but grew directly on the soft sediment.
An exception is in the coralline algal^bryozoan
facies, where it was found encrusting a single unilamellate, cyclostome bryozoan fragment. It dominates the bryozoan facies and the foraminiferal
facies. Mesophyllum sp. can be abundant in some
samples of the coralline algal facies and the coralline algal^bryozoan facies. It is particularly rare in
the coral^coralline algal facies.
Family Sporolithaceae, Verheij 1993
Sporolithon sp. (Fig. 3H,I)
Description : Growth form encrusting, thallus
200^800 Wm thick. The core portion is non-coaxial and ca. 60 Wm thick, sometimes up to 200
Wm; cell fusions occur. Filaments mainly curve
dorsally, rarely ventrally. The cell length is 18^
30 Wm (M = 25, SD = 4), the diameter 11^12
(M = 11, SD = 0). Cells of peripheral ¢laments
are rectangular and the cell rows are highly irregular. Trichocytes and growth rhythms are absent.
The cell length in peripheral ¢laments is 11^22 Wm
(M = 17, SD = 4), the diameter 7^11 Wm (M = 8,
SD = 1). Subepithallial initials and epithallial cells
are not preserved.
Tetrasporangial conceptacles are arranged in
sori with at least 30 conceptacles each in dorsoventral section. Paraphyses of one to four ¢laments are interspersed between the conceptacles,
each of them three cells long. The conceptacle
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99
Fig. 4. Autochthonous occurrence of Bergpeterl Quarry-SW section showing modal composition of all carbonate components,
coralline algal distribution, carbonate facies, and algal associations.
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height is 90^100 Wm, the diameter mostly 40 Wm.
Stalk cells, pores, and roof thickness are not measurable. The sori are raised about one half above
the thallus surface. Old sori are continuously
buried by peripheral ¢laments and not £aked
o¡. Carposporangial and sexual conceptacles are
unknown.
Occurrence: Sporolithon sp. accounts for 1% of
the algae in all samples, ranging from 0 to 12% of
the algae among the particular samples. It only
occurs in two samples of the autochthonous coralline algal and foraminiferal facies. Beside these
two facies it is only known from the allochthonous coral^coralline algal facies, where it is usually represented by isolated, fragmented crusts.
The encrusted substrates are mostly unknown,
but in one sample Sporolithon sp. encrusts a coral
fragment.
3.3.2. Identi¢cation key
Tetra/bisporangial conceptacles arranged in
sori: Family Sporolithaceae (1)
Tetra/bisporangial conceptacles not arranged in
sori: Family Corallinaceae (2)
(1) Family Sporolithaceae
(1a) Tetra/bisporangial conceptacles 90^100 Wm
high: Sporolithon sp. (Fig. 3H,I)
(2) Family Corallinaceae
(2a) Cells of contiguous ¢laments connected by
cell fusions ; tetra/bisporangial conceptacles uniporate: Subfamily Mastophoroideae (3)
(2b) Cells of contiguous ¢laments connected by
cell fusions ; tetra/bisporangial conceptacles multiporate: Subfamily Melobesioideae (4)
(3) Subfamily Mastophoroideae
(3a) Thallus dimerous with very large cells (palisade cells), postigenous ¢laments only occur
around conceptacles : Lithoporella melobesioides
(4) Subfamily Melobesioideae
(4a) Thallus non-coaxial ; growth rhythms in
perithallus present; tetra/bisporangial conceptacles 200^275U150^200 Wm; conceptacles roof
thickness 45^72 Wm; cell length in conceptacles
roof 11^20 Wm: Lithothamnion sp. A (Fig. 3A,
B)
(4b) Thallus non-coaxial; growth rhythms in
perithallus absent; tetra/bisporangial conceptacles
190^410U90^160 Wm; conceptacles roof thickness
31^49 Wm; cell length in conceptacles roof 5^9
Wm: Lithothamnion sp. B (Fig. 3C^E)
(4c) Thallus coaxial ; tetra/bisporangial conceptacles 520^640U170^200 Wm; conceptacle roof
thickness 60^75 Wm; cell length in conceptacles
roof approx. 9 Wm: Mesophyllum sp. (Fig. 3F,
G)
3.4. Distribution of coralline algae among
carbonate facies
Coralline algae are present in all facies, but they
dominate the coralline algal facies, coralline algal^bryozoan facies, and coral^coralline algal facies. The relative abundances of coralline algal
taxa are given in Figs. 4 and 5 and Table 1.
(1) The coralline algal facies is particularly
dominated by Lithothamnion sp. B. Lithothamnion
sp. A and Mesophyllum sp. are subordinate, while
Sporolithon sp. is rare.
(2) The coral^coralline algal facies reveals an
almost equal abundance of Lithothamnion sp. A
and B, although the latter is more abundant. It is
important to note, however, that this facies is
only known from one sample of the autochthonous occurrences. This is the only sample in
which Lithothamnion sp. A is absent. L. melobesioides, Mesophyllum sp., and Sporolithon sp. are
rare, although this is the only facies in which the
latter occurs in more than one sample.
(3) The coralline algal^bryozoan facies is dominated by Lithothamnion sp. A and Mesophyllum
sp. Lithothamnion sp. B is also present, while
L. melobesioides and Sporolithon sp. are absent.
(4) Coralline algae are under-represented in the
bryozoan facies and are characterised by fragmented branches of Lithothamnion sp. A and fragments of encrusting Mesophyllum sp. Other species are absent.
(5) The coralline algae of the foraminiferal facies are fragmented crusts of Sporolithon sp., Lithothamnion sp. A, and Lithothamnion sp. B.
Highly fragmented crusts of Mesophyllum sp. are
most abundant in this facies.
3.5. Growth forms of coralline algae
The studied coralline algal species show partic-
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101
Fig. 5. Allochthonous coralline algal localities including carbonate facies, coralline algal assemblages, and algal distribution.
º sterndorf and Kufsteiner Wald.
Above: isolated autochthonous localities of O
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Table 2
Growth features of coralline algae and their occurrences
Growth forms
Substrate
Unattached or detrital
thalli, respectively
other coralline algae
bryozoans
unknown
branches, rarely crusts
Lithothamnion sp. B
Mesophyllum
encrusting
encrusting to lumpy
and fruticose
encrusting to lumpy
encrusting
Sporolithon
encrusting
corals
¢ne-grained sediment,
rarely bryozoan
fragments
bryozoan fragments,
coral fragments
Facies
c
L. melobesioides
Lithothamnion sp. A
cc
cb b
f
L
E
L
F
F
branches, rarely crusts
only crusts
F
F
L
E
E
F
only crusts
E
E
F
L
F
F
E
Table shows the described coralline algal species, their growth forms after Woelkerling et al. (1993), the encrusted substrate, the
features of detrital occurrences, and the relative abundance of species in the particular carbonate facies after Nebelsick et al.
(2001). For abbreviations see Table 1.
F abundant; L present, E rare.
ular growth forms, which result in di¡erent types
of detrital thalli (Table 2). Lithoporella melobesioides only reveals encrusting growth forms; unattached or detrital occurrences, respectively, are
unknown. Growth forms of attached thalli of
Lithothamnion sp. A are encrusting to lumpy
and fruticose. Their unattached/detrital occurrences are, however, dominated by branching
forms, while encrusting habits are subordinate.
The same is true for Lithothamnion sp. B,
although fruticose growth forms are unknown.
Both Mesophyllum sp. and Sporolithon sp. only
reveal encrusting growth forms, and therefore
only crustose unattached/detrital habits are
known.
Lithothamnion sp. B, but other taxa are subordinate.
b Cluster 4 (M/LA) is dominated by Mesophyllum sp., which shows the highest abundance in
this cluster (48.8%), and Lithothamnion sp. A.
3.6. Hierarchical cluster analysis
Results from hierarchical cluster analysis reveal
¢ve distinct clusters (Table 1 and Fig. 6).
b Cluster 1 (LA/LB in Fig. 6) is dominated by
Lithothamnion sp. A, which accounts for 56.7% of
the algae, and a relatively high abundance of Lithothamnion sp. B (24%). Lithoporella melobesioides shows its highest abundance in this cluster.
b Cluster 2 (LB/LA) is dominated by Lithothamnion sp. B (39.4%) and Lithothamnion sp. A
(29.9%). Sporolithon sp. shows its highest abundance in this cluster (4.4%).
b
Cluster 3 (LB) is also dominated by
Fig. 6. Q-mode cluster analysis of coralline algal species and
designation of algal assemblages (compare Table 1). For abbreviations see Fig. 5.
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b Cluster 5 (M/DET) is dominated by Mesophyllum sp. and algal detritus; other taxa could
not be identi¢ed due to the poor preservation of
the algal detritus.
3.7. Coralline algal assemblages
Owing to the distinct distribution of taxa
among the clusters, our de¢nition of algal assemblages follows the cluster analysis (Fig. 6). This
section summarises the characteristics of the algal
assemblages named after the main taxa as well as
their distribution among sections and carbonate
facies. Samples refer to Figs. 4 and 5.
3.7.1. Cluster 1: Lithothamnion
sp. A^Lithothamnion sp. B assemblage (LA/LB)
Distribution : This assemblage is restricted to
allochthonous occurrences. It forms debris layers
in the Bergpeterl Quarry-B section (UIT 22^24
and 26; and UIT 30, respectively), and also occurs in the Bridge section (BP 6, 7).
Carbonate facies: The debris layers in which
this assemblage occurs correspond to three di¡erent carbonate facies: coral^coralline algal facies
(UIT 22^26; BP 6), coralline algal facies (UIT
30) and foraminiferal facies (BP 7).
Description and comparison: Lithothamnion sp.
A, which is the dominant species in this assemblage, is characterised by fragmented branches
and crusts in all facies. The one exception is in
the coralline algal facies, where it encrusts a single
bryozoan colony. Lithothamnion sp. B, which is
the second important species, can also form debris, but typically encrusts corals. If the encrusted
corals are fragmented, the fracture surfaces are
never encrusted.
All other taxa are rare. Both Mesophyllum sp.
and Sporolithon sp. can encrust fragmented bryozoans, while Lithoporella melobesioides encrusts
other coralline algae. Both of the taxa additionally show fragmented unattached branches and
crusts. In contrast to the other facies, the bioclasts
of the foraminiferal facies are never encrusted.
3.7.2. Cluster 2: Lithothamnion
sp. B^Lithothamnion sp. A assemblage (LB/LA)
Distribution : This assemblage is known from
103
the middle part of the autochthonous occurrence
of the section Bergpeterl Quarry-SW (IT 5, 6), as
well as from four di¡erent debris layers of the
allochthonous occurrences (BP 18, 19, 21; IT
13; IT 26; UIT 25).
Carbonate facies: This assemblage is restricted
to two facies. The allochthonous occurrences are
almost restricted to the coral^coralline algal facies
(BP 18, 19, 21; IT 26; UIT 25), while the autochthonous occurrences are typical for the coralline
algal^bryozoan facies (IT 5, 6).
Description and comparison: Algae of the autochthonous occurrences do not encrust other biota, but are only known as unattached thalli.
Lithothamnion sp. B only shows warty to lumpy
growth forms. While sample IT 5 shows fragmented thalli of this species, those of IT 6 are
not fragmented. The same is true for Lithothamnion sp. A, but this species can additionally form
horizontal crusts on the ¢ne-grained sediment,
with lateral extensions of several centimetres.
Mesophyllum sp. partially contributes to these
crustose successions. Lithothamnion sp. A is
more dominant in IT 6, which shows a higher
abundance of bryozoans.
Algae in the allochthonous occurrence of
the coralline algal^bryozoan facies are always
fragmented and unattached. However, those
of the coralline algal^coral facies characteristically encrust bioclasts. Unfortunately, many of
these encrusting specimens cannot be identi¢ed due to poor preservation. The analyses
of the identi¢able taxa show that Lithoporella
melobesioides can encrust other coralline algae,
Sporolithon sp. can encrust both corals and
bryozoans, and Lithothamnion sp. B encrusts
corals.
3.7.3. Cluster 3: Lithothamnion sp. B assemblage
(LB)
Distribution : Four of the ¢ve samples characterised by this assemblage are part of the autochthonous occurrences. This assemblage occurs at
the base of the autochthonous occurrence of the
Bergpeterl Quarry-SW section (IT3, 4) and is the
only known assemblage occurring in the two othº sterndorf (UIT 6)
er autochthonous facies of O
and Kufsteiner Wald (UIT 1). It is known from
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only one allochthonous occurrence of the Bridge
section (BP 20).
Carbonate facies: In the autochthonous occurrence of the Bergpeterl Quarry-SW section, this
assemblage is restricted to the coralline algal facies. The occurrences of the Bridge section and of
Kufsteiner Wald are part of the coralline algal^
º sterndorf is part of the focoral facies, that of O
raminiferal facies.
Description and comparisons: Lithothamnion sp.
B encrusts corals in all samples, but the latter are
frequently recrystallised and preserved as ‘ghost
structures’. Lithothamnion sp. A is especially rare
in this assemblage; in sample BP 20 it encrusts
bryozoans. Lithoporella melobesioides grows on
other coralline algae. Both the former species
and other taxa are represented by fragmented
thalli.
3.7.4. Cluster 4: Mesophyllum
sp.^Lithothamnion sp. A assemblage (M/LA)
Distribution : As in the LB assemblage, four of
the ¢ve samples characterised by this assemblage
are part of the autochthonous occurrences. In
the Bergpeterl Quarry-SW section, this assemblage occurs in the upper part of the section
(IT 7^10). It also occurs in a debris layer of
the allochthonous Bergpeterl Quarry-B section
(IT 27).
Carbonate facies: The M/LA assemblage in the
autochthonous occurrence occurs in the coralline
algal^bryozoan facies and the bryozoan facies. In
the allochthonous occurrence it is known from the
coralline algal facies. Fig. 4 shows that the abundance of Lithothamnion sp. A is related to the
abundance of bryozoans.
Description and comparisons : All taxa are
usually fragmented. Only Lithothamnion sp. A
encrusts bryozoans in the allochthonous occurrence.
3.7.5. Cluster 5: Mesophyllum sp.^detritus
assemblage (M/DET)
This assemblage is only known from one allochthonous layer of the Bergpeterl Quarry-B section (IT 24, 25) and is restricted to the foraminiferal facies. Only Mesophyllum sp. could be
identi¢ed. All algae are highly fragmented.
4. Discussion
4.1. Palaeoecological factors in£uencing coralline
algal distribution
The distribution patterns of crustose coralline
algal taxa as well as their growth forms and substrate relationships are potentially powerful tools
for palaeoenvironmental reconstructions. A number of both biological and physical factors are
known to in£uence coralline algal growth and distribution and are subsequently discussed in detail.
4.1.1. Biotic interactions and substrate
relationships
Biotic interactions include predation by grazers
and competition for available substrates. Grazing
is important both as a destructive agent as well as
having a positive e¡ect by removing fouling
agents (Steneck, 1986, 1994; Steneck et al.,
1991). The recognition of grazing in fossil material is, however, very di⁄cult (compare Nebelsick
and Bassi, 2000). Gastropods, which are potential
grazing agents, are abundant in the deeper-water
marls of the study area, but are very rare in the
shallow-water carbonates. This, however, may be
due to diagenetic bias with the complete leaching
of aragonitic skeletons in the carbonates.
Competitors for space with a high fossilisation
potential are represented by corals, bryozoans,
encrusting foraminifers and other coralline algae.
Coralline algal encrustation sequences are mostly
made up of monospeci¢c thin crusts, while complex encrustation sequences are rare. Corals and
bryozoans represent the most commonly observed
biotic substrates encrusted by coralline algae (Fig.
2A,G). Only Lithoporella melobesioides is restricted to the encrustation of other algae, but
this is not a common feature. The availability of
suitable substrate for encrustation is a palaeoecological factor that is strongly related to competition for available space. The generally coarse nature of the sediment means that suitable, relatively
stable, substrates are readily available for coralline algae. These include not only larger biogenic
components, but also terrigenous clasts. The success of Mesophyllum sp. seems to be independent
of hard substrate. Several samples show this spe-
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cies lying horizontally oriented directly on the
¢ne-grained soft substrate, without any fragmentation. Furthermore, there are no observed hard
substrates encrusted by Mesophyllum sp., except
for one single bryozoan fragment. This suggests
that Mesophyllum sp. was able to grow directly on
¢ne-grained, soft substrates. This growth mode
has already been suggested for Neogoniolithon
sp. from the Upper Eocene Alpine Foreland
(Rasser, 2000) and Lower Oligocene of Slovenia
(Nebelsick et al., 2000; Nebelsick and Bassi, 2000)
as well as for fossil and present-day peyssonneliacean algae (Basso, 1990; Rasser, 2001). Similar
features have been described by Bosence and Pedley (1982) and Bosence (1983). Present-day analogues among coralline algae are, to our knowledge, unknown.
In summary, the lack of complex encrustation
sequences suggests that competition for space is of
minor importance for the studied coralline algae.
However, the availability of suitable substrates for
particular taxa seems to be important. Finally, the
lack of encrustations of fractured surfaces implies
that encrustation took place before reworking,
most probably before or soon after the death of
the encrusted biota.
4.1.2. Water depth, light availability, and
hydrodynamic energy
The in£uence of water depth as a combination
of light availability and hydrodynamic energy can
be seen in the changing algal assemblages of the
autochthonous section (Fig. 4). Nebelsick et al.
(2001) investigated the relative depth distribution
of the studied carbonate facies. They suggested
that coralline algal facies, coral^coralline algal facies, and foraminiferal facies were deposited in the
same shallow water depth range, laterally adjacent
to one another. Towards deeper water, they grade
into the coralline algal^bryozoan facies and the
bryozoan facies (Fig. 7). This interpretation is
based on general basin development (ongoing
trangression), the change from coarser to ¢ner
sediments and the change in dominance from autotrophic and symbiotrophic to heterotrophic organisms (Lo«¥er and Nebelsick, 2001). Following
this interpretation, the distribution of taxa suggests that Lithothamnion sp. B lived in the shal-
105
lower water accompanied by corals, while Lithothamnion sp. A and Mesophyllum sp. are more
typical for deeper-water conditions, associated
with bryozoans. This coincides with the low hydrodynamic energy necessary for the growth strategy of Mesophyllum sp.
4.1.3. Background sedimentation
Finally, background sedimentation may in£uence coralline algal distribution, because a high
rate may cause the burial of algal thalli and
muddy suspension may reduce light availability
necessary for photosynthesis. Net sedimentation
rates are di⁄cult to analyse in the investigated
carbonates. Sedimentation of coarser siliciclastics
is of minor importance, but a muddy matrix is
common. Sedimentation rate, however, even in
areas of high mud sedimentation derived from
suspension, do not exceed 3^5 mm/yr (Ogorelec
et al., 1991) and therefore hardly surpasses
growth rates of up to 22 mm/yr recorded for
branching coralline algae (for review see Matsuda,
1989).
4.2. Relations between coralline algal taxa,
non-algal biota, and substrate
There seems to be a strong correlation between
algal taxa and other biota, which can be interpreted either as a dependence on the same palaeoecological factors or as a direct encruster/substrate relationship. As documented above, each
coralline algal species has its preferred substrate,
which is often represented by the skeletons of
other biota.
(1) Lithoporella melobesioides preferably encrusts other coralline algal taxa, most of which
could not be identi¢ed due to poor preservation.
Although this species is not abundant, it occurs
consistently in both autochthonous and allochthonous settings.
(2) Lithothamnion sp. B is the typical coral
encruster and unattached/fragmented algal thalli
are also most frequently associated with corals.
The autochthonous occurrences of this facies
with abundant corals are interpreted to indicate
shallow-water conditions (Nebelsick et al., 2001).
This either suggests that Lithothamnion sp. B pre-
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Fig. 7. Spatial distribution of coralline algal assemblages based on the facies reconstruction of Nebelsick et al. (2001). For abbreviations of assemblages see Fig. 5. Note that the debris £ows contain carbonate facies, which are also known from autochthonous settings (compare Table 1).
fers shallow-water habitats, or that corals are its
preferred substrate.
(3) Lithothamnion sp. A shows a strong relationship to bryozoans. It is the only species that
encrusts bryozoans and unattached/fragmented
algal thalli are mostly associated with them.
This implies that Lithothamnion sp. A preferably
encrusts bryozoans and/or that it is adapted to
water depths greater than that of Lithothamnion
sp. B.
(4) The substrate relationships of Mesophyllum
sp. are completely di¡erent from those of other
coralline algae in the studied sediments. They
are almost only found growing directly on ¢negrained substrates, and are most frequently associated with bryozoans. The abundance of bryozo-
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ans suggests an environment deeper than that of
Lithothamnion sp. B. This could, however, be explained not only by an adaptation to lower light
conditions, but also by low hydrodynamic energy
conditions associated with ¢ne-grained, soft substrates.
(5) The generally low abundance of Sporolithon
sp. precludes any statements concerning its preferred substrate or environment.
4.3. Comparison between coralline algal
assemblages and carbonate facies
The distinction of samples based on microfacies
analysis of component distributions on the one
hand (Table 1), and on the taxonomic distribution
of a single, albeit important component on the
other, shows di¡erent results concerning their distributions and interpretations. These are slight
with respect to facies successions, but more serious with respect to the origination of components
within allochthonous debris £ows.
4.3.1. Autochthonous occurrences
There are both consistencies and di¡erences in
the overlap between facies and coralline algal assemblages in the autochthonous Bergpeterl
Quarry-SW section (Fig. 4). The coralline algal
facies shows the same distribution as the Lithothamnion sp. B algal assemblage. The border between Lithothamnion sp. B^Lithothamnion sp. A
and the Mesophyllum^Lithothamnion sp. B algal
assemblages lies within the coralline algal^bryozoan facies. These di¡erences are related to the
problems of designating strictly de¢ned units
within continuous developments; the general
trends are, however, consistent with one another.
The succession of the Bergpeterl Quarry-SW
section, from the coralline algal facies to the coralline algal^bryozoan facies to the bryozoan facies
was interpreted as a deepening of the sedimentary
environment by Nebelsick et al. (2001). This implies that the succession of the coralline algal associations (LB to LB/LA to M/LB algal assemblage) also re£ects this deepening trend. It also
implies the formerly discussed depth dependence
of coralline algae: while Lithothamnion sp. B is
most typical for shallowest environments, Litho-
107
thamnion sp. A and Mesophyllum sp. are more
typical for relatively deeper environments (compare the ‘coralline algal distribution’ of Fig. 4).
This interpretation is supported by the isolated,
º sterndorf (Fig. 5),
autochthonous occurrence of O
where Lithothamnion sp. B (LB assemblage) is
most prominent in a coral^coralline algal facies.
This assemblage also occurs in the foraminiferal
facies of the autochthonous Kufsteiner Wald locality (Fig. 5), which is again attributed to a shallow-water environment (Fig. 7).
4.3.2. Allochthonous occurrences
The biotic composition of debris £ows suggests
that they are derived from the same facies types
that are preserved among the autochthonous facies (Nebelsick et al., 2001). An important question is, to what extent can the algal assemblages
within the debris £ows be traced to autochthonous assemblages? It has been shown that the
distribution of algal species and assemblages within allochthonous carbonates is related to palaeoecological parameters including substrate relationships, light availability, hydrodynamic energy and
sedimentation rates. The algal assemblages within
debris £ow can thus potentially serve as valuable
indicators of environments not preserved or exposed within autochthonous settings.
The purely allochthonous LA/LB algal assemblage as well as the LB/LA algal assemblage in
allochthonous samples are characteristic for the
coralline algal^coral facies. Bryozoan-bearing facies are characterised by M/LA and LB/LA algal
assemblages. This overlap between facies types
and algal assemblages may be in£uenced by the
substrate relationships between algal taxa and
other biota. Close relationships between algal species and non-algal components are obvious even
within the debris £ows. This is especially true for
the LA/LB algal assemblage, LB/LA algal assemblage and M/DET algal assemblage, which dominate the allochthonous outcrops.
In the Bridge section, the upper debris layers
(BP 18^21) correspond to the general facies and
algal composition of autochthonous occurrences.
They are all represented by coral^coralline algal
facies. The prevailing dominance of corals is re£ected by the dominance of Lithothamnion sp. B
PALAEO 3185 5-11-03
108
M.W. Rasser, J.H. Nebelsick / Palaeogeography, Palaeoclimatology, Palaeoecology 201 (2003) 89^111
(LB/LA and LB assemblages). The composition
of sample IT 13 corresponds to that of the middle
part of the autochthonous Bergpeterl Quarry-SW
section, showing a similar relative abundance of
algal taxa as well as belonging to the coralline
algal^bryozoan facies. The allochthonous sample
IT 26 also closely re£ects the composition of autochthonous occurrences : a high abundance of
corals (coral^coralline algal facies) is associated
with a high abundance of Lithothamnion sp. B
(LB/LA assemblage). The high relative abundance
of Lithothamnion sp. A is associated with a corresponding prevalence of bryozoans.
Other assemblages from allochthonous occurrences do not re£ect those from autochthonous
carbonates. A contradiction is present in the lower debris layers in the Bridge section (BP 6 and 7).
These samples represent the coral^coralline algal
and foraminiferal facies with, however, a dominance of Lithothamnion sp. A (LA/LB assemblage). There are, however, two features that
could explain this contradiction (compare Table
1): these samples are among those with the highest abundance of lithoclasts (21 and 45%), and are
among those with the lowest abundance of coralline algae (11 and 17%). The ¢rst feature indicates
a high degree of reworking, which may have
caused a mixture of debris from di¡erent environments ; the second feature suggests that the coralline algae may not be very indicative as environmental indicators due to their low abundance.
The lower debris layers of the Bergpeterl
Quarry-B section represent the coral^coralline algal facies with two di¡erent algal assemblages.
The composition of UIT 25 with an LB/LA algal
assemblage corresponds to features of autochthonous occurrences in that they show a high amount
of corals combined with a dominance of Lithothamnion sp. B. The algal composition of UIT
22^23^24^26, however, which show an LA/LB algal assemblage, again represents a contradiction.
As in BP 6 and 7, however, they show very high
amounts of lithoclasts (up to 29%).
The samples IT 24 and 25 belong to the foraminiferal facies with, however, an M/DET algal
assemblage. As in the autochthonous occurrence
of Kufsteiner Wald, this facies contains bryozoans
associated with Mesophyllum sp. The algal assem-
blage is, however, completely di¡erent as well as
being extremely fragmented. The debris layer IT
27 belongs to the coralline algal facies, but contains an M/LA algal assemblage. This is, again, a
combination unknown from autochthonous occurrences, although it is again characterised by
the high fragmentation of Mesophyllum sp. thalli.
The allochthonous sample UIT 30 belongs to
the coralline algal facies (Nebelsick et al., 2001),
but contains an LA/LB algal assemblage. This
seems to pose a contradiction as this facies is
usually dominated by Lithothamnion sp. B alone.
This contradiction can, however, be explained by
the high abundance of bryozoans in this sample
which, as shown above, are closely associated
with a dominance of Lithothamnion sp. A.
4.4. Provenance analysis of debris £ows using algal
assemblages
The comparison of coralline algal assemblages
from autochthonous and allochthonous localities
allow eight of the 13 debris £ows to be correlated
to environments preserved in the autochthonous
facies. The remaining ¢ve samples show a low
abundance of coralline algae ( 6 17%), which
may reduce the possibilities of recognising algal
assemblages in the ¢rst place. There are, however,
two features shared by these samples : (1) a high
amount of lithoclasts, and (2) an extremely high
degree of algal thallus fragmentation. Both these
features suggest that substantial reworking led either to a mixing of algal remains from di¡erent
primary environments and/or to sorting during
debris £ow transport, both resulting in the atypical algal associations.
The quantitative approach based on the relative
abundance of coralline algal taxa clearly separates
primary algal assemblages (LB, LB/LA ; M/LA)
from those representing the atypical algal assemblages (LA/LB and M/DET) as seen in the cluster
analysis. The atypical algal assemblages (LA/LB
and M/DET) are restricted to debris £ows. The
fact, however, that the primary algal assemblages
are found in both in situ autochthonous localities
as well as in the transported allochthonous sediments suggests that algal assemblages can indeed
survive the mixing and transport processes asso-
PALAEO 3185 5-11-03
M.W. Rasser, J.H. Nebelsick / Palaeogeography, Palaeoclimatology, Palaeoecology 201 (2003) 89^111
ciated with the debris £ows. This suggests that
even those algal assemblages present within debris
£ows can be useful in analysing primary facies
relationships given that enough attention is given
to taxonomic identi¢cation and quantitative treatment of the algal assemblages.
5. Conclusions
Hierarchical cluster analysis of components
within the di¡erent facies (Nebelsick et al., 2001)
did not reveal any preferential occurrence of coralline algae as a whole with any other components. This is due to the ubiquitous occurrence
of coralline algae in every facies. The dissemination of algal taxa among facies, however, reveals
distinct distribution patterns.
Five coralline algal species, belonging to four
genera, are identi¢ed: Lithoporella melobesioides,
Lithothamnion sp. A, Lithothamnion sp. B, Mesophyllum sp., and Sporolithon sp. An open nomenclature is used due to the uncertainties in fossil
coralline algal taxonomy.
Two main factors that in£uenced the distribution of studied coralline algal taxa are: (1) suitable substrates and (2) water depth. Substrate
preferences are (a) corals for Lithothamnion sp.
B, (b) bryozoans for Lithothamnion sp. A, (c)
¢ne-grained substrate for Mesophyllum sp., (d)
other coralline algae for L. melobesioides. Substrate relationships for Sporolithon sp. could not
be discerned. The following associations to water
depth are found: (a) Lithothamnion sp. B is most
typical for very shallow water, while (b) Lithothamnion sp. A and Mesophyllum sp. B are more
typical for relatively deeper-water conditions.
Ecological parameters for L. melobesioides and
Sporolithon sp. could not be assessed due to their
low abundance.
Hierarchical cluster analysis allows the distinction of ¢ve coralline algal assemblages, which are
named after the most prominent taxa. Among
these ¢ve, Mesophyllum sp.^detritus assemblage
(M/DET) and Lithothamnion sp. A^Lithothamnion sp. B (LA/LB) are restricted to allochthonous
occurrences, while Lithothamnion sp. B^Lithothamnion sp. A (LB/LA), Lithothamnion sp. B
109
(LB), and Mesophyllum sp.^Lithothamnion sp. A
(M/LA) are known from both autochthonous and
allochthonous settings. Comparisons with carbonate facies and non-algal components reveal a distinct deepening upward trend among the succession from LB to LB/LA and M/LB algal
assemblages.
Most algal assemblages present in the allochthonous samples can be correlated to autochthonous settings. Exceptions with atypical association
of coralline algal taxa are found in allochthonous
samples containing the LA/LB, M/DET algal assemblages. These are accompanied by two features : a high abundance of lithoclasts and a
very high fragmentation of coralline algal thalli.
This may be related to mixing of components
from di¡erent primary environments and/or sorting processes during debris £ow transport.
Acknowledgements
We thank S.-B. Lo«¥er (Tu«bingen), H. Ortner
(Innsbruck), W.E. Piller (Graz) and V. Stingl
(Innsbruck) for help with ¢eld work. We are
also indebted to the reviewers, D. Bosence (London) and J. Braga (Granada), whose careful reading and critical comments helped to increase the
quality of this paper. J.N. was supported by the
Sonderforschungsbereich (SFB) 275 of the German Science Foundation (DFG) ; M.R. was supº sterreichiported by the ‘Jubila«umsfond der O
schen Nationalbank’, Project No. 6456 during
¢eld work and by the Austrian Science Foundation (FWF, Project P-14707 GEO).
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