Original paper
Die Oberdevon-Flora der Bäreninsel - 5. Gesamtübersicht
[The Upper Devonian Flora of Bear Island]
Schweitzer, Hans-Joachim
Palaeontographica Abteilung B Band 274 Lieferung 1-6 (2006), p. 1 - 191
259 references
published: Apr 7, 2006
Abstract
The Upper Devonian of Bear Island has been subdivided in three series (Horn & Orvin 1928, Kaiser 1970, 1971), which can be easily distinguished based on their lithology and biostratigraphy. The Misery Series is exposed on the eastern part of the island from Røedvika to Kapp Levin and comprises (Famennian) Fa2a-Fa2c. The Seamless Sandstone Series follows from Kapp Levin to Framnes. Its lower part belongs to Fa2c based on the spore content. The upper part is devoid of fossils and appears to belong to Tn1aγ (sensu Conil et al. 1967). The same age applies for the Tunheim Series, which is exposed from Framnes to almost Kapp Olsen with some interruptions (compare Text-fig. 1). The Tn1ag corresponds to the Etroeungt-Stage (Strunian) and is of latest Devonian age. The division of the Upper Devonian (Røedvika Formation) as suggested by Worsley & Edwards (1976) into Vesalstranda-, Kapp Levin-, and Tunheim Member is not followed, because it ignores the biostratigraphic evidence that correlates well with the lithological boundaries of Kaiser. The Misery Series was deposited under limnic conditions, the Tunheim Series at least partly under paralic conditions. Palaeoecological features of both series are discussed and the different composition of the floras is illustrated with vegetation sketches (Text-figs 2, 4). The macrofloras of the Misery and Tunheim Series are markedly different: Misery Series: Sublepidodendron heerii, Sphenophyllum tenerrimum, Cephalopteris mirabilis, Cephalopteris keilhaui, Cephalopteris tunheimensis, Cephalopteris squarrosa, Cephalopteris miserymontis, Sphenocyclopteridium belgicum, Archaeopteris macilenta Tunheim Series: Codonophyton epiphyticum, Pseudolepidodendropsis carneggianum, Jurinodendron kiltorkense, Lepidosigillaria? macrocicatricosa, Pseudobornia ursina, Cephalopteris keilhaui, Cephalopteris tunheimensis, Cephalopteris squarrosa, Archaeopteris halliana All spores and macroremains reported for the Upper Devonian of Bear Island are summarised. In addition, information is provided on the stratigraphic distribution of the taxa described in the systematic part. Thallophyta - Codonophyton epiphyticum Nathorst - Emended diagnosis: Delicate plant, up to 5 cm long, mostly associated with Pseudobornia ursina. Life form epiphytic or saprophytic. Thallus a plectenchyme that consists of parallel thread-like strands, which in most cases form a main axis. Main axis with densely spaced lateral organs, which are up to 0.1 mm thick and up to c. 10 mm long. Lateral organs mostly more or less recurved, appearing massive, however also composed of several thread-like strands. Complete lateral organs, expanded distally to be trumpet-shaped, terminating in a disk-like organ that is 0.3 mm in diameter. The surface of the disk shows up to six crater-like pits that have a diameter of 0.05 mm and are surrounded by 0.01 mm thick walls. In these cavities probable reproductive organs developed, but are never preserved. The systematic placement of the species therefore remains uncertain. Pteridophyta - Lycopsida - Four species. Two species, Sublepidodendron heerii and Pseudolepidodendropsis carneggianum are without a ligule and parichnos. Jurinodendron (Cyclostigma) kiltorkense and Lepidosigillaria? macrocicatricosa display parichnos and the latter also a ligule. In J. kiltorkense a ligule has not been observed but could be covered by the leaf cushion. Sublepidodendrales - Wang et al. (2002) proposed to separate tree-like from herbaceous Protolepidodendrales because of the more highly evolved wood anatomy. On the other hand it is not useful to include the former entirely into the Lepidodendrales because they lack a ligule and parichnos. Therefore, a new order, Sublepidodendrales, is proposed. Sublepidodendron (Nathorst) Hirmer - Sublepidodendron heerii nov. comb. Nathorst assigned three different names to the single lycopsid plant of the Misery Series: Macrostachya heerii and Bothrodendron (Cyclostigma) brevifolium (1902), and Porodendron isachsenii (1914). Based on findings of more complete material in 1967, P. isachsenii was recognized as belonging to Sublepidodendron. Further examination showed that all three species belong to Sublepidodendron heerii. Emended diagnosis: Arborescent, branching lycopsid. Stem at least 11 cm in diameter. Arrangement of leaf cushions pseudoverticillate but they sometimes appear verticillate, cushions present only in younger branches, fusiform, up to 2.5 mm long, length to width ration ca. 4:1. Leaf scars in uppermost part of cushion, with a rounded upper margin and acutely elongate towards the base, covering approximately half of the cushion. Vascular bundle scar in upper part of the leaf scar. Leaves very thin, up to 10 mm long by 1 mm wide, with the widest part slightly above the middle, and then tapering to the apex. Vascular bundle situated medially. In older axes, leaves abscising together with the cushions and therefore only narrow elliptic scars with acute ends present. Scars arranged in a parastichous pattern, pseudoverticillate. Between the scars a delicate reticulate sculpture occurs on the stem surface. Pseudolepidodendropsis Schweitzer - Pseudolepidodendropsis carneggianum (Heer) Schweitzer: In a previous work Schweitzer (1969) demonstrated that stem remains with cushions that had traditionally been called Lepidodendron (Bothrodendron, Cyclostigma) wijkianum and branches with undeveloped cushions that had been called Lepidodendron (Bothrodendron, Cyclostigma) carneggianum belong to the same species. This plant is restricted to the Tunheim Series and is described in detail. The only other occurrence of this species is in southwestern Siberia. The stem bears alternating leaf cushions mostly in pseudoverticillate arrangement, which are elongate rhombic in outline and somewhat tapering at both ends. The inverted triangular, obliquely upward pointing leaf scar is situated somewhat above the middle, bearing in its centre a small vascular bundle scar, but no parichnos scars. A median ridge leads from the leaf scar to the cushion base. The surface of the cushion is smooth. Longitudinally striated zones extend between them. With increasing ontogenetic age the cushions lose their elongate rhombic shape and gradually assume an inverted egg-shaped outline. However, the shape of the cushions can be altered considerably by secondary compression. The leaf cushions begin to develop on thicker branches only, and they are not present on higher order branches. However, the leaf scars show the same outline and the same sculpture as on the stem. The alleged parichnos scars mentioned by Nathorst (1902) are preservational artifacts. Nothing can be said about the habit of the plant since only unbranched remains of stems and branches have been found. They only show that the body of wood was very small in comparison to the thickness of the stem. Lepidodendrales - Jurinodendron Doweld - Haughton (1859) used Cyclostigma for the best-known Upper Devonian lycopsid plant although this name had already previously been used for modern plants, first by Endlicher (1842) for a genus in the Apocynaceae. Therefore, following the rules of nomenclature Doweld (2001) introduced the genus name Jurinodendron. Jurinodendron kiltorkense (Haughton) Doweld Contrary to the opinion of Jongmans (1931) and Pantič (1960) only one species of the genus is found on Bear Island. It is identical with the species from Ireland, which makes the name Cyclostigma ursina superfluous. Jurinodendron kiltorkense is by far the most abundant lycopsid plant and played a major role in the formation of coal on Bear Island. It appears for the first time in the overlying shales of the youngest Misery seam (one twig), but is among the dominating elements in the Tunheim Series together with Pseudobornia ursina and Archaeopteris halliana. Based on fragments of stems and of branches from Bear Island, and leafy branches and fructifications from Ireland, a reconstruction of the whole plant in its natural proportions is possible. The thickest stem from Bear Island measures 20 cm in diameter, while stems from Ireland have a diameter up to 30 cm. The apical part of the stem is formed by an anisotomous branching. Using a tapering of the stem of c. 2 cm per 1 m, a stem length of 5 to 6 m can be estimated for the Bear Island plant; and 7 to 8 m for the plant from Ireland. In addition, the crown can be estimated as c. 2 m high, based on the length and the angles that branches form with the stem. This means a total height of the tree of 7 to 10 m. A short summary of the known facts is provided on page 49. For details see descriptions of the individual organs. The species is restricted to the Strunian (Etroeungt) in all localities, while the geographic distribution is not entirely clear. Only the occurrences in Ireland, Bear Island, and Southwestern Siberia are confirmed. Lepidosigillaria Kräusel et Weyland - Lepidosigillaria? macrocicatricosa sp. nov.: Only two specimens of this species have been found. One is a small fragment of a twig with the leaf cushions not fully developed, which Schweitzer (1969) erroneously ascribed to Jurinodendron kiltorkense. The other is a fragment of the stem with conspicuously large cushions. The two fossils from the Tunheim Series cannot be assigned to a particular known genus, but they do not contain enough information to establish a new genus. Therefore, they are preliminarily placed within the genus Lepidosigillaria. The leaf cushions show the closest resemblance to this genus. They are characterised by a ligule depression and a vascular bundle with two parichnos laterally. However, in contrast to other members of Lepidosigillaria, the leaf cushions are not arranged on typical rhytidolepous longitudinal ridges. Diagnosis: Lycopsid plant belonging to Lepidodendrales. Leaf cushions alternating, in slightly ascending spirals (parastichous), with distinct orthostichous pattern. The formation of ridges, as in the rhytidolepous sigillarian lycopods, is lacking. Leaf cushions becoming larger during secondary growth. Leaf scar indistinct, vascular bundle situated in the centre of the cushion, and with two lateral parichnos. In young cushions ligule depression immediately above the vascular bundle, in older ones more distant to it and situated in a triangular-rhombic area from which a median ridge (or groove) runs to the vascular bundle. Holotype: The specimen illustrated in Pl. 20, Fig. 1 and in Text-fig. 28a. Derivatio nominis: Referring to the conspicuously large leaf scars. Stratum typicum: Tunheim Series, uppermost Famennian (Strunian = Etroeungt = Tn 1 aγ sensu Conil et al. 1967). Locus typicus: Bear Island. Tunheim, above the A-seam. Material: Fragment of stem, Swedish Museum of Natural History, Department of Palaeobotany, Stockholm, fragment of a branch, Institute for Systematic Botany, University of Jena. Sphenopsida: Two species have been reported for Bear Island, Sphenophyllum tenerrimum and Pseudobornia ursina. They display all the characters of modern Equisetaceae, except for the triarchous-exarchous vascular bundle of Sphenophyllum. In both species the axes are composed of clear nodes and internodes, lateral organs are restricted to the nodes, which are strengthened by diaphragms. Therefore, it can be assumed that their growth habit corresponded to that of living horsetails. An apical meristem, with one apical meristematic cell, intercalary cell division restricted to the nodes, and longitudinal cell elongation in the internodes are highly specialised features within the pteridophytes. The morphological disparity between the Sphenopsida and other pteridophytes makes it difficult to identify evolutionary relationships. Moreover, the combination of these three features means it is unlikely that they arose from Devonian plants with pseudoverticillately arranged lateral organs. It is suggested that ancestors to Sphenopsida were pre-Devonian. All Lower and Middle Devonian genera that are considered ancestral to Equisetaceae are critically evaluated. It is shown that no genus can be assigned to Sphenopsida without doubt. Closest similarities with Sphenopsida are found in Honseleria verticillata. Sphenophyllales - Sphenophyllum Koenig - Sphenophyllum tenerrimum Ettingshausen - Nathorst (1902) referred one Sphenophyllum from the Misery Series to S. subtenerrimum. He distinguished this species from the Lower Carboniferous S. tenerrimum by its higher number of leaves per whorl, the longer internodes, the more conspicuously swollen nodal lines, and the slightly higher insertion of the lateral branches. Examination of additional specimens from 1967, however, showed that all these characters are not suitable for distinguishing the two species, and that, therefore, S. subtenerrimum ought to be rejected. Pseudoborniales - Pseudobornia Nathorst - Pseudobornia ursina Nathorst: This is the most characteristic plant of Bear Island, where it is very abundant in the Tunheim Series, particularly in Kolbukta. In the monograph from 1969 P. ursina was reconstructed as a tree, 15 to 20 m tall, with upwards-curved branches at least 3 m long. These branches were interpreted as rhizomes by Nathorst, which led to an erroneous interpretation of this plant. Schweitzer's (1969) reconstruction was based on the finding of a stem that was exposed over the length of 10 m with a lower diameter of 60 cm and an upper diameter of 25 cm. Branches had been reconstructed from fragments. Despite numerous finds Gensel & Andrews (1984) argued that Pseudobornia was a shrub or small tree. In the present study a branch is described that was excavated and measured in 1967. The size of the branch confirms the original reconstruction. All organs building the plant are discussed. The reconstruction of the fertile organs (Text-fig. 53b) is from a specimen examined by the author in Liège in the 1960s. Unfortunately, this specimen has subsequently been lost. The sporophylls and sporangia are similar to those of Lilpopia crockensis. Despite this, Pseudobornia does not display closer affinities to sphenophylls and cannot be assigned to Sphenophyllopsida, because of its completely different anatomy. Filicopsida - Coenopteridales: Coenopteridian ferns of Bear Island belong to the genus Cephalopteris, except for Sphenocyclopteridium belgicum. So far, five species have been reported, of which two (C. mirabilis, C. keilhaui) have already been described by Nathorst, while three others (C. tunheimensis, C. squarrosa, C. miserymontis) are described here. All are characterised by normally trifurcately branched main axes, and bifurcately branched higher orders. The branches, including the lateral organs, alternate by 180°. The two branches of each pair originating from the main axis form an angle of c. 90°. This mode of branching parallels that of Rhacophyton but with much longer distances between pinnules resulting in sparsely pinnate afrondso. Only C. keilhaui shows a tendency towards the density seen in Rhacophyton. Within the genus a change occurs from three-dimensionally branching, telome-like lateral organs to normal, entire-margined, sphenopteridian pinnules. This is achieved through planation and parenchymatic fusion (cf. Text-fig. 87). Fructifications are known only from C. mirabilis, C. keilhaui, and C. tunheimensis. They form multiple branching sporangiophores with terminal sporangia. Cephalopteris Nathorst - Emended diagnosis: Coenopteridian ferns resembling Rhacophyton, but the vegetative parts at a lower phylogenetic level and apparently herbaceous (stems and secondary growth have not been reported). Main axes normally trifurcately branched, in some species (C. tunheimensis and ?C. squarrosa) possibly also bifurcate. Trifurcate branching sometimes also observed in first order branches. Branches of second order only with bifurcate branching. Normally, all organs alternating at 180°, in rare cases at smaller angles. Sterile lateral organs in some species more or less three-dimensionally branched, rigid or very delicate, in other species developed as sphenopteridian pinnules. Fertile organs originating from distal parts of the plants. Sporangiophores arranged in highly reduced branching systems, inserted at the bases of branches or sometimes more distally, bending or curved upwards, like in Rhacophyton forming dense clusters of cigar-shaped to pointed to beaked-sporangia. Cephalopteris mirabilis Nathorst: This species is confined to the Misery Series. Creeping rhizomes are recorded for the first time, and in contrast to the aerial shoots they have a surface with longitudinal ridges. Main axes with a median vascular bundle originate from rhizomes. From the main axis pairs of sterile branches arise proximally and fertile branches distally. The common base of each branch has a decurrent extension. In addition, aphlebia-like organs occur below sterile branches and strongly recurved sporangiophores below fertile branches. Further sporangiophores, but no aphlebia, occur at divisions more distally on the fertile branches. The sterile lateral organs and aphlebia are divided into a dichotomous series of thin, three-dimensionally branched segments. Sporangiophores consist of highly reduced, anisotomous-isotomous branching systems and bear terminal sporangia that are cigar-shaped, slightly pointed, and recurved. Cephalopteris keilhaui (Nathorst) Schweitzer: Cephalopteris keilhaui is the most abundant fern on Bear Island. At the same time it shows the greatest stratigraphic range. Occurring in the basal layers of the Misery Series, its abundance increases towards the higher layers of the Tunheim Series. The numerous new findings make necessary an emendation of Nathorst's diagnosis. The architecture of the fern is essentially the same as in C. mirabilis. However, the axes are covered with emergences, which are not preserved in most cases, and leave wart-like scars. Based on their presence also smaller fragments are easily identified. Furthermore, the aphlebia-like organs appear to be missing. Occasionally dormant buds are observed. Sterile pinnules are deeply dissected, their segments conspicuously wider than in C. mirabilis and most probably already two-dimensional, resulting in a markedly "fern-like" appearance of branching system (Text-fig. 71). The sporangiophores partly originate from the main axis, but more often at various positions on the first order axes. They branch in up to five anisotomous dichotomous series and are not curved to such an extent as in C. mirabilis. The atropous, erect sporangia are arranged in dense clusters with a pointed to slightly beaked apex (cf. Text-fig. 70). Emended diagnosis: Fern with the mode of branching typical of the genus. Axes covered with emergences. These only preserved in rare cases, but leave wart-like to elongate scars. Aphlebia-like organs not reported. Pinnules sphenopteroid, deeply dissected, segments wider than in C. mirabilis, most probably at a single level. Terminal segments pointed. Sporangiophores partly on main axes, more often on first order branches at different positions, branching in up to five series of dichotomies, less incurved as in C. mirabilis. Sporangia in dense clusters, atropous and erect, apex pointed to slightly beaked, c. 3 to 4 mm long. In situ spores probably belonging to Perotrilites luteolus. Cephalopteris tunheimensis sp. nov.: Cephalopteris tunheimensis is the phylogenetically most advanced fern of Bear Island. This species is rather rare, but can be found in both the Misery and the Tunheim Series. It is a much stronger plant than the two previous species. The main axis is up to 20 mm wide, straight, with longitudinal ridges but otherwise smooth. Branches of first order are solitary rather than in pairs, and irregularly spirally arranged. They are of different thickness and branch trifurcately or bifurcately. They become pinnate only distally and in second order branches. The branching mode is less fixed than in C. mirabilis and C. keilhaui. The sphenopteridian pinnules branch in up to four series of dichotomies to form cuneiform notched lobes. As in C. keilhaui the sporangiophores originate from the main axes and end in densely spaced sporangia. Diagnosis: Robust coenopteridian fern with straight main axis, c. 20 mm wide, with characteristic longitudinal ridges. First order branches mainly solitary, more rarely in pairs, arranged in an irregular spiral, of unequal width, and partly trifurcate, partly bifurcate; as main axis with longitudinal ridges. First order branches becoming pinnate in their upper parts, second order branches pinnate. Typical pinnules wider than long, the largest 20 x 15 mm, the smallest 7 x 5 mm, arranged in up to four series of dichotomies, forming terminal lobes. Lobe cuneiform, notched; venation fan-like. Sporangia on pedicellate sporangiophores originating from axes, 3.5 to 4 mm long, 2 mm wide at the base, with an elongate end. Holotype: The specimen figured in Pl. 41, Fig. 1. Derivationominis: After the mining village Tunheim. Stratum typicum: Tunheim-Series, uppermost Famennian (Strunian = Etroeungt = Tn 1 ag sensu Conil et al. 1967). Locus typicus: Bear Island, between MaÊkestauren and Kapp Olsen. Material: Swedish Museum of Natural History, Department of Palaeobotany, Stockholm. Cephalopteris squarrosa sp. nov.: Robust fern with the same stratigraphic distribution as C. tunheimensis but even more rare. Diagnosis: Robust coenopteridian fern, with rather rigid branching and erect main axis, c. 20 mm wide. Main axis with branches that are solitary (?) or in pairs (?) forming steep angles with main axis. All branches first to sixth order alternating at c. 180°. First order branches mostly trifurcate, remaining branches bifurcate. Surface of axis and branches with longitudinal ridges (not as prominent as in C. tunheimensis), otherwise smooth. Starting with branches of second order a median vascular bundle visible. Fourth and higher order branches form lateral organs that attain more than 7 cm of length, and branch three-dimensionally in an incurved manner terminating in an apical bifurcation. The incurved branching pattern means that they are often broken. Pinnules absent. No fructifications observed. Holotype: The central specimen figured in Pl. 46, Fig. 1 and in Text-fig. 83 Derivatio nominis: Squarros (latin): rigid. Stratum typicum: Tunheim Series, uppermost Famennian (Strunian = Etroeungt = Tn 1 aγ sensu Conil et al. 1967). Locus typicus: Bear island, between Måkestauren and Kapp Olsen. Material: Swedish Museum of Natural History, Department of Palaeobotany, Stockholm. Cephalopteris miserymontis sp. nov.: The species has only two records from the vicinity of Brettingsdalen. It illustrates that the genus also produces delicate species. After the better preserved specimen had been lost, only a sterile branch of first order remains. Diagnosis: Coenopteridian fern. Main axis unknown. First order branch thin and slender, tapering from 3.3 mm to 1.3 mm along a length of 28 cm, irregularly branching, displaying a zig-zag course from node to node. Bipartite at the end and merging into a tuft composed of numerous thin axes. Second order branches trifurcate and bifurcate, alternating at 180°, third order branches bifurcate. At the base finely dissected organs (originally aphlebia) present, but not always preserved. Third order branches with delicate, pinnule-like elements. All branches ending in tufts. Fructification unknown. Holotype: The specimen figured in Text-fig. 86. Derivatio nominis: After the locality Mount Misery. Stratum typicum: Misery Series, upper Famennian (Fa 2c). Locus typicus: Bear Island. Misery Fjellet between Brettingsdalen and Kapp Levin. Material: Swedish Museum of Natural History, Department of Palaeobotany, Stockholm. Sphenocyclopteridium Stockmans - Sphenocyclopteridium belgicum Stockmans Only a single specimen is known from the Misery Series. The longest axis measures 8 cm and is covered with tiny emergences that leave scars similar to those of Cephalopteris keilhaui. Sterile pinnules correspond in size and outline to those from Belgium. They are smaller than those of C. tunheimensis and differ from this species also by their round shape and the almost palmate lobes with strong veins. The systematic position of the species is uncertain, because only small and sterile fragments have been found. It cannot be ruled out that it belongs to Cephalopteris. Progymnospermopsida - Archaeopteris Lesquereux: The knowledge of this genus has increased considerably since 1960, both with respect to its anatomy and morphology. A number of recent studies is reviewed and compared to the material from Bear Island. On Bear Island the genus is represented by two species, A. macilenta and A. halliana. Archaeopteris intermedia Nathorst is identical with A. macilenta. Archaeopteris macilenta Lesquereux: The species is most characteristic of the lower parts of the Misery Series that is now covered by a huge landslide. The frond-like leaves have a long lanceolate shape and are on average 55 to 60 cm long. They are distichously attached to branches that have been described as Rhizomopteris nordenskiöldi by Nathorst (1902). Sterile and fertile fronds occur, but mixed fertile and sterile ones are also present. The fossils from Bear Island correspond in all features with the ones described by Phillips et al. (1972) from North America. Because the rare material could not be prepared the phylogenetically so important aberrantly developed fronds (cf. Text-fig. 92) could not be demonstrated. Archaeopteris halliana (Goeppert) Stur: In contrast to A. macilenta, A. halliana is a typical floral element of the Tunheim Series. The earliest occurrence is from the uppermost shale of the youngest Misery coal seam (as is the case for Jurinodendron kiltorkense), but there is no palynological evidence for a floral change in this horizon. The nomenclature of this species is so complicated that it is necessary to explain in detail why the specific epithet halliana has priority over roemeriana used by Nathorst (1902). Of a 1.2 m long branch fragment only the tuber-shaped base and part of its continuation could be recovered while the part with the fronds inserting immediately disintegrated. The surface of this branch shows the longitudinal ridges typical of all archaeopterids. A similarly preserved fragment of a branch has been described as Anarthrocanna goepperti by Nathorst (1902). Axes devoid of bark ± identified as ?Heterangium by Nathorst ± have a more or less smooth surface with a faint longitudinal pattern from the tracheids of the secondary wood. The shape of the bipinnate fronds is linear lanceolate. They are, however, longer and wider than in A. macilenta, being on average 70 cm long. The observations of Carluccio et al. (1966) and Phillips et al. (1972) are inconsistent with respect to the arrangement of Zwischenfiedern and pinnules. According to the former it is spiral, according to the latter decussate opposite. The material from Bear Island has Zwischenfiedern and pinnules that are spirally arranged. On Bear Island fertile and partly fertile fronds are rare when compared to sterile ones. Moreover, they are so badly preserved that it was necessary to use text-figures from Phillips et al. (1972).
Kurzfassung
Allgemeiner Teil: Das Oberdevon der Bäreninsel wird nach den Vorschlägen von Horn & Orvin (1928) und Kaiser (1970 u. 1971) in drei Serien untergliedert. Sie lassen sich sowohl lithologisch als auch biostratigraphisch gut gegeneinander abgrenzen. Die Misery-Serie steht auf der Ostseite der Insel von der Røedvika bis zum Kapp Levin an und umfasst das Fa2a±Fa2c. Die Flözleere Sandstein-Serie folgt vom Kapp Levin bis zur Framnes. Ihr unterer Bereich gehört nach dem Sporeninhalt noch zum Fa2c, der obere, fossilleere, dürfte jedoch schon in das Tn1aγ zu stellen sein. Dieses Alter hat auch die Tunheim-Serie, die von der Framnes mit einigen Unterbrechungen bis fast zum Kapp Olsen ansteht (vgl. Abb. 1). Das Tn1aγ entspricht der Etroeungt-Stufe (Strunium) und ist noch oberdevonischen Alters. Der von Worsley & Edwards (1976) vorgenommenen Gliederung des Oberdevons (Røedvika-Formation) in Vesalstranda-, Kapp Levin- und Tunheim Member wird nicht gefolgt, weil sie die biostratigraphischen Fakten und die damit besser in Übereinklang stehende lithologische Grenzziehung von Kaiser ignoriert. Die Misery-Serie ist unter limnischen, die Tunheim-Serie zumindest temporär unter paralischen Bedingungen abgelagert worden. Auf die paläoökologischen Verhältnisse beider Serien wird ausführlich eingegangen und die unterschiedliche Zusammensetzung der Floren anhand von Vegetationsbildern dargestellt (Abb. 2 u. 4). Die Makrofloren von Misery- und Tunheim-Serie unterscheiden sich beträchtlich: Misery-Serie: Sublepidodendron heerii, Sphenophyllum tenerrimum, Cephalopteris mirabilis, Cephalopteris keilhaui, Cephalopteris tunheimensis, Cephalopteris squarrosa, Cephalopteris miserymontis, Sphenocyclopteridium belgicum, Archaeopteris macilenta Tunheim-Serie: Codonophyton epiphyticum, Pseudolepidodendropsis carneggianum, Jurinodendron (Cyclostigma) kiltorkense, Lepidosigillaria? macrocicatricosa, Pseudobornia ursina, Cephalopteris keilhaui, Cephalopteris tunheimensis, Cephalopteris squarrosa, Archaeopteris halliana Alle bisher im Oberdevon der Bäreninsel nachgewiesenen Sporen und als Makroreste erhaltenen Pflanzen werden tabellarisch erfasst, von den letzteren auch die stratigraphische Verbreitung (Tab. 2 u. 3).
Keywords
lithology • biostratigraphy • Røedvika • Kapp Levin • macrofloras • Oberdevon