Biogeography in the Sub-Arctic. Группа авторов

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СКАЧАТЬ 6894 [as Fagus castaneaefolia Ung. in Heer (1868; Pl. XLVI, fig. 3a)]. (B) Fagopsiphyllum groenlandicum (Heer) Manchester, from Upper Atanikerluk A, MGUH 6269 [as Castanea ungeri Heer in Heer (1883; Pl. LXIX, fig. 3)]. (C) Fagopsiphyllum groenlandicum (Heer) Manchester, from Upper Atanikerluk A, MGUH 6270 [as Quercus grönlandica Heer in Heer (1883; Pl. LXIX, fig. 4)]. (D) Eotrigonobalanus sp., from Upper Atanikerluk B, MGUH 6349 [as Quercus laharpii Gaud. in Heer (1883; Pl. LXXIV, fig. 2)]. (E) Eotrigonobalanus sp., from Upper Atanikerluk B, MGUH 6372 [as Pterocarya denticulata Web in Heer (1883; Pl. LXXVI, fig. 1)]. (F) Eotrigonobalanus sp., from Upper Atanikerluk B, MGUH 6390 [as Laurus reussii Ettingsh. in Heer (1883; Pl. LXXVII, fig. 7)]. (G) Eotrigonobalanus sp., from Upper Atanikerluk B, S109006 [as Laurus primigenia Ung. in Heer (1880; Pl. III, fig. 8a)]. (H) Eotrigonobalanus sp., from Upper Atanikerluk B, S109107. (See colour plate section for colour representation of this figure.)

Macrofossils of the Upper Atanikerluk A flora comprise a large number of leaves resembling various modern genera of Fagaceae. Among these, Fagopsiphyllum is fairly abundant (Figure 5A to C, see Plate section). Figure 5C shows a typical leaf of Fagopsiphyllum; in contrast, the leaves shown in Figure 5A and B, although falling into the morphological variability of Fagopsiphyllum, clearly are reminiscent of leaf types encountered in modern taxa of Quercus section Cyclobalanopsis, and of the castaneoid genera Lithocarpus and Castanopsis (see illustrations in Camus 1929 et seq.). Another distinct leaf type is morphologically similar to both leaves from the Paleogene of North America (Dryophyllum‐like leaves; Jones and Dilcher 1988) and to Eotrigonobalanus from Europe (Kvaček and Walther 1989; Figure 5D to H). The pollen spectrum of the Upper Atanikerluk A flora has not yet been studied with high resolution scanning electron microscopy (SEM). However, the contemporaneous Agatdalen flora and the middle Eocene Hareø flora have recently been investigated and yield a remarkably high diversity of Fagaceae pollen (Grímsson et al. 2015, 2016a). Pollen unambiguously referable to Fagus, along with macrofossils of this genus, provide reliable evidence of this genus in the Cenozoic of Greenland (Figure 6A and B and Figure 7A). In addition, pollen of various Castaneoideae (according to Ørsted; see Praglowski 1984) is documented (Figure 6C and D). Numerous types of Quercus pollen represent various sections within the genus: Sect. Lobatae (Figure 6I and J), Lobatae/Quercus (white or red oaks; Figure 6K and L) and sect. Protobalanus (see Grímsson et al. 2015). Apart from this, additional Fagaceae pollen types represent extinct or ancestral lineages, Eotrigonobalanus (Figure 6G and H), Paraquercus (see pl. 12, Figures 1 to 5 in Grímsson et al. 2016b), and the pollen shown in Figure 6E and F. The latter is indistinguishable from pollen of the modern Quercus sect. Ilex (according to Denk and Grimm 2010; Denk et al. 2017; synonymous with subgenus Heterobalanus according to Menitsky 1984, 2005). This type of pollen has been suggested to be plesiomorphic within oaks (Denk and Grimm 2009a). In the Neogene of Europe, pollen of this type co‐occurs with leaves of Quercus drymeja Unger and Q. mediterranea Unger belonging to Quercus sect. Ilex (Denk et al. 2010b). Based on the modern distribution of this group of oaks from the Mediterranean area to south of the Himalayas and Southeast Asia (Menitsky 1984; Denk and Grimm 2010) and of the absence of foliage indicative of this group, the pollen encountered in the Eocene Hareø flora of Greenland may originate from an extinct and 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 СКАЧАТЬ