Biogeography in the Sub-Arctic. Группа авторов
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ancestral member of Quercus that had retained the plesiomorphic pollen. This would be in accordance with the presence of Fagaceae foliage with unclear generic/infra‐generic affinities in the Palaeocene to Eocene of Greenland.
The presence of Aponogeton in the Eocene of West Greenland (Grímsson et al. 2014) is recorded both in the palynological (Figure 6O and P) and macrofossil records of Hareø (Figure 7B and C). The foliage associated with the pollen partly recalls foliage from the Eocene/Oligocene Renardodden Formation of Svalbard ascribed to the extinct genus Haemantophyllum by Budantsev and Golovneva (2009, plate 88, Figures 5 and 6) and originally described as Alsima macrophylla by Heer (1876). The fossil pollen from Hareø clearly suggests closer affinities to Aponogeton than to any other members of the Alismatales (Grímsson et al. 2014).
Faroe Islands
The Faroe Islands are patchy sub‐aerial remnants of a previously extensive Paleogene lava sequence that is considered part of the Brito‐Arctic Igneous (floral) Province (BIP; Figure 1). The strata composing the Faroes are named the Faroe Islands Basalt Group (Passey and Jolley 2009). The stratigraphic thickness of exposed rock is ca. 3.2 km, with additional ca. 3.4 km thick subsurface units documented from boreholes. Recently, the stratigraphy and age of the Faroe Islands has been summarized and revised (cf. Riisager et al. 2002; Passey and Jolley 2009). The strata are subdivided into seven formations. The Lopra Formation is the basal volcanic construction, known only from boreholes, and is succeeded by the geochemically different Beinisvørð Formation. Most of the few reported plant macrofossils from the Faroe Islands (e.g. Hartz 1903; Rasmussen and Koch 1963) originate from the upper half of this formation, in an outcrop on the island Mykines (Mykines flora). The lavas of the Beinisvørð Formation are overlain by sedimentary rocks of the Prestfjall Formation. These sedimentary rocks contain two coal seams and associated silt and sandstones (Rasmussen and Noe‐Nygaard 1969). The palynological content of this formation (Prestfjall flora) has been studied by Laufeld (1965) and Lund (1989) from outcrops on the island Suðuroy. The sedimentary rocks of the Prestfjall Formation are succeeded by pyroclastics and lavas of the Hvannhagi and Malistindur Formations and the volcaniclastics and lavas of the Sneis and Enni Formations (e.g. Passey and Jolley 2009). Radiometric dating of lavas from the Faroe Islands and corresponding lavas on Greenland show that basalts below the Prestfjall Formation are ca. 60–56 Ma and volcanics above the Prestfjall Formation are ca. 56–54 Ma (e.g. Waagstein et al. 2002; Storey et al. 2007; Passey and Jolley 2009). Stratigraphic correlation of the plant‐bearing sedimentary rock units on Mykines with Waagstein et al. (2002) suggest they are ca. 58 Ma and of late Palaeocene age (late Thanetian), but those of the Prestfjall Formation are just under 56 Ma and of early Eocene age (earliest Ypresian; Figure 2).
Figure 6 Eocene fossil pollen from Hareø, West Greenland. (A, B) Fagus sp. (C, D) Castaneoideae gen. et spec. indet. (E, F) Quercus plesiomorphic pollen type of Quercus; identical to extant pollen of Quercus sect. Ilex. (G, H) aff. Eotrigonobalanus sp. (I, J) Quercus sp. (K, L) Quercus sect. Lobatae/Quercus. (M, N) Spirematospermum sp. (O, P) Aponogeton sp.
Figure 7 Eocene fossil leaves from Hareø, West Greenland. (A) Fagus sp., S110238. (B) Aponogeton sp., S110339. (C) Aponogeton sp., S110337.
Plant macrofossils have been known from the Faroe Islands since 1901 (see Hartz 1903). Until now the only detailed description is of Metasequoia vegetative long and short shoots (Rasmussen and Koch 1963; Figure 3E). Remains of other Cupressaceae have also been recorded and believed to represent Sequoia, Taxodium and Juniperus. The few fragmentary angiosperm leaf fossils recovered have been considered unidentifiable (Hartz 1903; Rasmussen 1925; Rasmussen and Koch 1963). Despite the current lack of macrofossils from the Faroe Island, two previous light microscopic palynological studies by Laufeld (1965) and Lund (1989) suggest that a rather diverse palaeovegetation existed during the accumulation of the early Eocene coal‐bearing Prestfjall Formation.
The early Eocene palynological assemblage was characterized by swamp forests and riparian elements comprising several ferns, taxodiaceous Cupressaceae (intermittently amounting to over 30% of the palynological assemblage), Juglandaceae and Betulaceae. On more mesic sites Fagaceae, Juglandaceae and other eudicots may have thrived along with Pinus, Sciadopitys and possibly Sequoia.
Island of Mull
The Palaeocene flora of Mull, Scotland, originally described by Gardner (1887) is the only Paleogene BIP flora that has been revised in more recent years (Boulter and Manum 1989; Figures 1 and 2). The age of the intrabasaltic plant‐bearing sediments of Mull has been radiometrically dated at 60–58 Ma (Chambers and Pringle 2001).
Among riparian and wetland elements, the ferns Dennstaedtia, Onoclea and Osmunda were widespread in Paleogene Arctic plant assemblages, commonly co‐occurring with Metasequoia. Among the diverse gymnosperms, Ginkgo gardneri Florin represents a lineage more closely related to Mesozoic ginkgoes than to the Cenozoic Ginkgo adiantoides (Ung.) Heer from Europe and Svalbard (Denk and Velitzelos 2002). Further, Amentotaxus, cf. Cephalotaxus, Glyptostrobus, Elatocladus (with affinities to modern Taxodium and Sequoia), Metasequoia and Pinus and cf. Tsuga are recorded (Boulter and Kvaček 1989; Kvaček 2010). Platanites hebridicus Forbes is an extinct Platanaceae distinct from the coeval Platanus schimperi (Heer) Saporta and Marion of Gelinden (Belgium; Mai 1995) and Platanus aff. leucophylla (Unger) Knobloch from western Greenland. The genus Platanites has also been recorded from the Paleogene of Saskatchewan (Canada; McIver and Basinger 1993) and possibly from the Eocene of north‐western Wyoming (Crane et al. 1988). In addition, few pentafoliate leaves and leaflets belong to the extinct Platanus subgenus Glandulosa Kvaček, Manchester and Guo. These were assigned to Platanus fraxinifolia (Johnson and Gilmore) Walther by Boulter and Kvaček (1989) in contrast to the trifoliate leaves of P. bella from Greenland.
Common elements of Mull, mostly shared with the floras of Greenland, are Trochodendroides (and rare Ziziphoides), betulaceous leaves of Corylites [shared with Svalbard], Fagopsiphyllum groenlandicum (Heer) Manchester [as Fagopsis groenlandica (Heer) Wolfe; shared with the floras of Greenland and Svalbard], Ushia olafsenii (Heer) Boulter and Kvaček, Juglandiphyllites spp., foliage with affinity to Fagaceae (Castanopsis, Lithocarpus, Quercus sect. Cyclobalanopsis [as Camptodromites spp.] and Macclintockia. A number of taxa not found in other BIP floras are the distinct foliage of Davidoidea (similar to Platanaceae, Hamamelidaceae and Euptelea)