The Middle Late Miocene Floras - A Window into the Regional Vegetation Surrounding a Large Caldera more

Chapter 7 The Middle Late Miocene Floras – A Window into the Regional Vegetation Surrounding a Large Caldera Abstract Terrestrial fossils from Late Miocene sediments in the Mókollsdalur area are mainly known for their insect fauna. Plant fossils and the sedimentological context suggest that most of the macrofossils deposited at Mókollsdalur originate from trees and shrubs that grew on the slopes around a caldera lake in the highlands. Abundant fossils of aquatic crustaceans, insects, and plants suggest that the lake and adjacent areas were a diverse ecosystem at the time of deposition. Forests covering the slopes were dominated by Fagus with a few evergreen elements in the understorey (Ilex, Rhododendron). In contrast, the palynological record points to the presence of mixed oak forests in areas behind the mountain ridge surrounding the caldera. The poor representation of herbaceous elements in the pollen record may point to a filter effect against pollen influx from surrounding areas into the lake. Slope exposure may have determined the presence of Fagus or Quercus as is also seen today in cool temperate regions of the northern hemisphere. Overall, the climate appears to be more diversified than in the older floras with relatively warmer humid conditions windward of the mountains or in sheltered areas close to the lake and cooler more continental conditions leeward of the mountains. 7.1 Introduction The sedimentary rocks of the Skarðsströnd-Mókollsdalur Formation are between 9 and 8 Ma (middle to late Tortonian, middle Late Miocene; McDougall et al. 1984). Sedimentary rocks of this formation were discovered in the late nineteenth century by Thoroddsen (1896) when he studied the lignites of the Northwest Peninsula. The full extension of this formation was later established by Bárðarson (1918), Schwarzbach (1955), and particularly Akhmetiev et al. (1978). Although the presence of well-preserved plant fossils, especially leaves, in this formation was already known from the reports of Bárðarson (1918), Schwarzbach (1955), and Áskelsson (1961), leaf fossils were not described and figured before the 1970s (Friedrich et al. 1972; Akhmetiev et al. 1978; Friedrich and Símonarson 1982; Símonarson and Friedrich 1983; Denk et al. 2005; Grímsson and Denk 2005). The Skarðsströnd-Mókollsdalur Formation has become well-known mainly because of its T. Denk et al., Late Cainozoic Floras of Iceland, Topics in Geobiology 35, DOI 10.1007/978-94-007-0372-8_7, © Springer Science+Business Media B.V. 2011 369 370 7 The Middle Late Miocene Floras (9–8 Ma) animal fossils, which are generally very rare in Miocene sediments of Iceland. From Mókollsdalur, several nicely preserved insects have been found (Friedrich et al. 1972), but only a single taxon has been described, the hickory aphid, Longistigma caryae Harris (Heie and Friedrich 1971). Water fleas, aquatic crustaceans, most likely representing species of Daphnia, are also abundant (Símonarson 1981). In this chapter, we use evidence from plant macrofossils, pollen and spores to reconstruct the vegetation in Iceland 9–8 Ma. The Late Miocene vegetation of Iceland is compared to modern vegetation types, and for some key taxa, ecological and climatic requirements are estimated using their potential modern analogues. Based on this, the climate for Iceland in the middle Late Miocene is evaluated and illustrated with climate diagrams. Taxonomic affinities of fossil taxa from Iceland to coeval fossils in Eurasia and North America are established and used to describe patterns of plant migration to Iceland during the Late Miocene. The availability of a land bridge between Iceland and Europe/North America during this time period is evaluated in view of the palaeobotanical record. 7.2 Geological Setting and Taphonomy The Skarðsströnd-Mókollsdalur Formation (9–8 Ma; McDougall et al. 1984) is exposed at the southeastern part of the Northwest Peninsula (Fig. 7.1a) and is the youngest fossiliferous sedimentary rock formation exposed there. This formation can be traced along outcrops from southwest to northeast (Fig. 7.1b) along the Skarðsströnd coastline (Tindafjall locality), into Gilsfjörður fjord and up the Brekkudalur valley, over the Steinadalsheiði highland, down into Mókollsdalur (Hrútagil locality, Fig. 7.1c) and Þrúðardalur on the Kollafjörður fjord, and onwards to Ennishöfði (Broddanes locality). The sedimentary rocks composing this formation are quite variable, mostly sandstones and siltstones with associated lignites. The thickness ranges from 5 to 35 m in general (Akhmetiev et al. 1978), except for at the Hrútagil locality and other outcrops in the Mókollsdalur valley, where the sedimentary rocks are over 120 m thick (Friedrich et al. 1972; Grímsson and Símonarson 2006). Hrútagil in Mókollsdalur is the most important locality of this formation and has the highest number of plant macrofossils. Otherwise, identifiable plant remains are rarely found outside the Mókollsdalur area, and the same is true for animal fossils. The lowest part of the sedimentary rocks in Hrútagil is composed of thick hyaloclastite units with interlaminated breccias and sandstones. The middle part is mostly composed of sandstones and siltstones, and in the upper part siltstones, claystones and organic-rich sediments become prominent, both diatomite and lignites. It is in this upper part where most of the plant and animal fossils have been collected. The whole section is interlaminated by various types of volcanic sediments, reflecting a rather frequent eruption history during accumulation. Tectonic displacement, volcanic constructions, and sedimentary rock types in the Mókollsdalur valley and the Hrútagil gully reflect the palaeo-topography and the most important geological features in the area during time of accumulation. 7.2 Geological Setting and Taphonomy 371 Fig. 7.1 Map showing fossiliferous localities of the 9–8 Ma formation. (a) bedrock geology (see Fig. 1.10 for explanation), (b) extension of sedimentary rock formation, (c) Hrútagil locality (Geological background modified after Jóhannesson and Sæmundsson 1989; altitudinal lines from Landmælingar Íslands 1994) 372 7 The Middle Late Miocene Floras (9–8 Ma) Various indications point to the presence of an extinct volcanic system with a central volcano in the area surrounding the Mókollsdalur, Þrúðardalur, and Steinadalur valleys (Fig. 7.1c). First, intermediate intrusions with associated radiating dykes and fault swarms are seen around Mókollsdalur (Jóhannesson and Sæmundsson 1989). Second, acid and intermediate volcanic sedimentary units are preserved as various tuff types in the area (Friedrich et al. 1972; Akhmetiev et al. 1978). This central volcano was a large caldera (Jóhannesson and Sæmundsson 1998) and the sediments seen in Hrútagil and other outcrops in Mókollsdalur accumulated in the freshwater lake of this caldera. Judging from the geography and geological history of the area, the caldera was positioned in the highlands at a considerable distance from the coast when it was active. The freshwater lake in the central part of the caldera was bound by a steep cliff and surrounded by a mountain ridge formed by the eruptions. Macrofossil plant remains in the sediments of this caldera originate from trees and shrubs growing on the hillsides and slopes facing the lake of the caldera. In contrast, the palynological record captures not only the vegetation surrounding the caldera lake, but also outside the caldera. Apparently, the lake was a diversified ecosystem as reflected by the repeated diatomite units and the frequently found water fleas in the upper part of the sedimentary rock sequence in Hrútagil and Mókollsdalur. 7.3 Floras, Vegetation, and Palaeoenvironments The floras of the Skarðsströnd-Mókollsdalur Formation are markedly less speciesrich than those from the older Tröllatunga-Gautshamar Formation (42 versus 99 taxa; Table 7.1, Fig. 7.2, Plates 7.1–7.23). Most fossil taxa belong to woody angiosperms (19 taxa), followed by mosses and ferns (eight taxa) and conifers (nine taxa). The low number of herbaceous plants (five taxa) is probably the result of taphonomic processes rather than a reflection of the lack of herbaceous vegetation. Table 7.1 Taxa recorded for the 9–8 Ma floras of Iceland Skarðsströnd-Mókollsdalur Formation Taxa Lycopodiaceae Lycopodiella sp. Lycopodium sp. Huperzia sp. Osmundaceae Osmunda sp. Polypodiaceae Polypodiaceae gen. et spec. indet. 1 Polypodiaceae gen. et spec. indet. 6 Incertae sedis – unassigned spores Monolete spore, fam., gen. et spec. indet. 1 Monolete spore, fam., gen. et spec. indet. 2 Pollen + + + + + + + + Leaves RP DM 1a 1a 1a 1a 1a 1a 1a 1a (continued) 7.3 Floras, Vegetation, and Palaeoenvironments Table 7.1 (continued) Skarðsströnd-Mókollsdalur Formation Taxa Pinaceae Abies sp. Larix sp. Picea sect. Picea Pinus sp. 1 (Diploxylon type) Pinus sp. 2 (Haploxylon type) Pseudotsuga sp. Tsuga sp. 1 Tsuga sp. 2 Sciadopityaceae Sciadopitys sp. Apiaceae Apiaceae gen. et spec. indet. 5 Aquifoliaceae Ilex sp. 2 Asteraceae Asteraceae gen. et spec. indet. 1 Betulaceae Alnus cecropiifolia Betula cristata cf. Carpinus Calycanthaceae aff. Calycanthaceae Cornaceae Cornus sp. Ericaceae Rhododendron sp. 2 Fagaceae Fagus gussonii Quercus infrageneric group Quercus sp. 1 Juglandaceae Cyclocarya sp. Pterocarya sp. Myricaceae Myrica sp. Poaceae Poaceae gen. et spec. indet. 1 Ranunculaceae Thalictrum sp. 2 Ranunculaceae gen. et spec. indet. 2 Salicaceae Salix gruberi Sapindaceae Acer crenatifolium subsp. islandicum Acer askelssonii Trochodendraceae Tetracentron atlanticum 373 Pollen + + + + + + + + + + + + + + Leaves RP DM 2a 2a 2a 2a 2a 2a 2a 2a 2a 1b 1b 1a +D + + + + +D +D 1a, 2a 1a 2a 1b + + + + + (+) (+) + + + + + (+)2 (+)2 + + + + +D +D + +D 1b 1a?, 2a 2b, 3 2b, 3 2a 2a 1b 1b, 2a 1b 1b 1a 2a 2a + + +D 2a (continued) 374 Table 7.1 (continued) Skarðsströnd-Mókollsdalur Formation Taxa 7 The Middle Late Miocene Floras (9–8 Ma) Pollen Leaves RP DM Ulmaceae Ulmus section Ulmus sp. + + + D 2a Incertae sedis – Magnoliophyta Dicotylophyllum sp. D + ? Dicotylophyllum sp. E + ? Angiosperm fam. et gen. indet. A + ? L leafy axis, A fruit attached to leafy axis, D fruit dispersed, RP reproductive structure, + organ present, + original description of species based on this organ, (+) organ belonging to genus but uncertain to which of the species, (+) 2 indicating number of pollen types possibly belonging to the eponymous morphotaxon, DM dispersal mode: 1a wind long distance (anemochory), 1b bird long distance (endozoochory), 2a wind short distance (anemochory), 2b animals short distance (exozoochory), 3 dyschory Fig. 7.2 Distribution of life forms and higher taxa among the plants from the 9–8 Ma formation. Height of columns indicates number of taxa The mountain ridge surrounding the caldera lake may have provided a vital barrier to pollen influx from outside the caldera. Apart from this bias, the macrofossil and palynological record allows for drawing a fairly precise picture of the palaeovegetation surrounding the caldera in the Mókollsdalur area. Six vegetation types can be distinguished (Table 7.2; Fig. 7.3). Only a few taxa are typical of flooded areas, possibly suggesting that the lake shores were not inhabited by extensive swamp forests. A poor riparian community may have contained a small number of canopy tree species (Alnus, Pterocarya) with some herbaceous ferns, fern allies, and angiosperms in the understorey. Shrubs such as aff. Meadows and shrublands Huperzia sp. Apiaceae gen. et spec. indet. 5 Asteraceae gen. et spec. indet. 1 Poaceae gen. et spec. indet. 1 Ranunculaceae gen. et spec. indet. 2 Thalictrum sp. 2 Rocky outcrop forests Huperzia sp. Lycopodium sp. Larix sp. Picea sect. Picea Pinus sp. 1, 2 Pseudotsuga sp. Tsuga sp. 1, 2 Tetracentron atlanticum Table 7.2 Vegetation types and their components during the middle Late Miocene of Iceland Vegetation types 9–8 Ma Temporally flooded lake margin Montane forests Pterocarya sp. Lycopodiella sp. Fagus gussonii Lycopodium sp. Quercus sp. 1 Polypodiaceae gen. et spec. indet. 1, 6 Alnus cecropiifolia Rhododendron sp. 2 Abies sp. aff. Calycanthaceae Myrica sp. Ulmus sp. Larix sp. Osmunda sp. Picea sect. Picea Poaceae gen. et spec. indet. 1 Foothill forests Pseudotsuga sp. Pterocarya sp. Lycopodium sp. Tsuga sp. 1, 2 Ranunculaceae gen. et spec. indet. 2 Polypodiaceae gen. et spec. indet. 1, 5 Sciadopitys sp. Salix gruberi Picea sect. Picea Acer crenatifolium subsp. islandicum Sciadopitys sp. Cyclocarya sp. Well-drained lowland forests and Ilex sp. 2 Fagus gussonii lake margins Alnus cecropiifolia Ilex sp. 2 Lycopodium sp. Betula cristata Rhododendron sp. 2 Osmunda sp. cf. Carpinus sp. Tetracentron atlanticum Polypodiaceae gen. et spec. indet. 1, 6 Rhododendron sp. 2 Ulmus sp. Picea sect. Picea Fagus gussonii Acer askelssonii Quercus sp. 1 Acer crenatifolium subsp. islandicum Cyclocarya sp. Alnus cecropiifolia Acer askelssonii Betula cristata Acer crenatifolium subsp. islandicum aff. Calycanthaceae cf. Carpinus sp. Tetracentron atlanticum Cornus sp. Ulmus sp. Myrica sp. AzonAL VeGeTATIon zonAL VeGeTATIon The palaeoecology of fossil species is reconstructed from their sedimentological context and ecology of modern analogues 376 7 The Middle Late Miocene Floras (9–8 Ma) Fig. 7.3 Schematic block diagram showing landscapes and vegetation types for the middle Late Miocene of Iceland. See Table 7.2 for species composition of vegetation types Calycanthaceae and Myrica may have grown in such narrow strips of temporallyflooded lake margins. Well-drained areas at some distance from the lake were probably occupied by moderately species-rich broadleaved deciduous forests with a small proportion of conifers and evergreen shrubs in the understorey (Rhododendron, Ilex). Main trees were Fagus gussonii, Acer spp., Betula, cf. Carpinus, and Ulmus. Fagus gussonii is by far the most abundant element among the macrofossils, represented by leaves, bud scales, cupules, and nuts. This species is also the most abundant in the pollen record. This evidence points to an autochthonous origin of these fossils. In contrast, not a single leaf of Quercus has ever been recovered from the 9 to 8 Ma sediments. At the same time, Quercus is among the most common elements in the pollen record. This pattern may suggest that slopes facing different directions and/or having different microclimates sustained different variants of broadleaved deciduous forests. Fagus dominated forests would have been on the slopes facing the caldera lake (Fig. 7.4), whereas Quercus probably inhabited areas behind the mountain ridge surrounding the caldera lake (Fig. 7.5). Similarly, Fagus is typical of shady slopes in temperate regions of Central Europe, while deciduous species of Quercus are found on more sun-exposed slopes (Ellenberg 1986). Well-drained foothill forests were probably fairly similar to montane forests with the exception of a higher 7.3 Floras, Vegetation, and Palaeoenvironments Fig. 7.4 Schematic transect of a broadleaved deciduous forest facing the caldera lake. Fagus gussonii is the dominating tree species 377 378 7 The Middle Late Miocene Floras (9–8 Ma) Fig. 7.5 Schematic transect of a broadleaved deciduous forest outside the caldera. Quercus is the dominating tree species 7.4 Ecological and Climatic Requirements of Modern Analogues 379 proportion of conifers in the montane forests. In view of the absence of conifer taxa in the macrofossil record in the Mókollsdalur area, these montane forests may have thrived at elevations higher than the slopes surrounding the caldera. In contrast, few seeds of Picea have been recovered in the Skarðsströnd area (Tindafjall locality; Akhmetiev et al. 1978). Meadow and shrubland vegetation is represented only by spore and pollen taxa, indicating they were not present in close vicinity to the caldera lake. The general scarcity of herbaceous elements in the pollen record points to a filter against pollen influx from the surrounding areas into the caldera lake, emphasizing the local character of the fossil assemblage from the 9 to 8 Ma formation. 7.4 ecological and Climatic Requirements of Modern Analogues Most of the potential modern analogues of the taxa found in the Mókolldalur area have a high climatic tolerance (Chap. 13, Appendix 13.1). In contrast, various elements that were also present in the older formations (e.g. Ilex, Rhododendron, and Fagus) require mild climatic conditions (MAT >5°C). Some taxa of the 9–8 Ma formation have been discussed in previous chapters (Fagus, Sciadopitys, and Cyclocarya in Chaps. 4, 5 and 6). Acer askelssonii is similar to modern species of Acer sect. Platanoidea comprising several Eurasian species and of sect. Acer with a disjunct distribution in Eurasia, western and eastern North America (van Gelderen et al. 1994). Closer similarities are found with the western Eurasian species Acer platanoides L. (sect. Platanoidea) and the North American A. saccharum Marsh. (sect. Acer). Acer platanoides has a wide range from northern Europe to eastern and southeastern Europe, including the Caucasus, where it forms a part of the rich broadleaved deciduous forests from the lowlands to about 1,500 m a. s. l. (Hegi 1926). This species covers a wide range of climates (Cfa, Cfb, Dfb, Dfc according to Köppen; Kottek et al. 2006) with MAT 2–15°C. Acer saccharum has a disjunct distribution in eastern and western North America, including Mexico and Guatemala. It grows in lowlands and uplands to ca 1,000 m a. s. l. in its eastern range and up to 2,500 m a. s. l. in its western range, mainly under a Dfb climate with MAT −1.1–15.8°C (Thompson et al. 1999). Pterocarya sp. from the 9 to 8 Ma formation is represented by leaves, leaflets, winged nutlets, and pollen. At present, the genus Pterocarya comprises six species, one in Asia Minor and five in East Asia. Two extant species are comparable to the fossil from Iceland. Pterocarya macroptera Batalin has winged nuts very similar to the ones recovered from the Mókollsdalur area (Grímsson et al. 2005). Pterocarya fraxinifolia (Lam.) Spach has leaflets with a very similar morphology to the fossil specimens. Pterocarya macroptera has a large distribution from Tibet in the west to Zheijang in the east, south of 35°N (Flora of China Editorial Committee 1999). It grows in moist forests and along mountain streams in Central China, between 1,100 and 380 7 The Middle Late Miocene Floras (9–8 Ma) 3,500 m a. s. l. The species thrives in a wide variety of climates, ranging from warm temperate (Tmin ³ −3°C) to snow climates (Tmin < −3°C), fully humid to winter dry, and hot to warm to cool summers (Cfa, Cfb, Cwa, Cwb, and Dwb and Dwc climate types according to Köppen; Kottek et al. 2006; Chap. 13, Table 13.1) with MAT 2.5–19.8°C. Pterocarya fraxinifolia is an Asian Minor species, where it typically occurs along the seashores of the Black and Caspian Seas, normally growing below 1,000 m a. s. l. In the Zagros Mountains, Iran, the species is found in altitudes up to 1,700 m a. s. l. (Akhani and Salimian 2003). Pterocarya fraxinifolia is an element of lowland riparian forests and of rich mixed broadleaved deciduous forests on mountain slopes. It typically thrives under a Cfa and Cfb climate (Dsa and Dsb in eastern Anatolia and the Zagros Mountains) with MAT 8.1–18.1°C (Utescher and Mosbrugger 2009). Cultivated trees flower and fruit in Scandinavia (Stockholm, MAT ca 6°C). Pollen of Quercus recovered from the 9 to 8 Ma formation belongs to either Quercus infrageneric group Quercus (white oaks) or Quercus infrageneric group Lobatae (red oaks; Denk and Grimm 2010). Among modern oaks, white oaks and red oaks have the most northern and most continental distribution (Camus 1936– 1938, 1938–1939, 1952–1954). Red oaks have their centre of diversity in Mexico and Central America, but some species can cope with cool temperate climates with severe winter frosts (e.g. Q. rubra L., MAT −1.1 to 19.4°C; Thompson et al. 1999). White oaks have a similar range as red oaks in North America, but extend further into cold continental areas (e.g. Q. macrocarpa Michaux, MAT −1.5 to 21.8°C, Jensen 1997; Nixon and Muller 1997; Thompson et al. 1999). In Eurasia, white oaks are clearly the most cold-tolerant members of oaks with some species (Q. robur L., Q. mongolica Fisch. ex Ledeb.) extending into areas with MAT close to the freezing point with severe frosts during the winter. Quercus robur, being a potential modern analogue of the fossil taxon, occurs in various climate types (mainly Cfb and Dfb according to Köppen; Kottek et al. 2006) with MAT 3.3–15°C. Overall, a Cfb to Dfb climate can be inferred for the 9–8 Ma formation. Modern climate stations that are comparable to the middle Late Miocene of Iceland are shown in Fig. 7.6. Lowlands might have experienced milder climates with more evenly distributed precipitation (Cf climates according to Köppen; see Fig. 7.6, 2) with MAT between 8° and 10°C. In the interior, more continental conditions caused slightly lower MAT and possibly colder winters (Df climates; compare Fig. 7.6, Gothenburg, Cfb and Klagenfurt, Dfb). 7.5 Taxonomic Affinities and origin of newcomers As in the older floras, most taxa encountered in the 9–8 Ma formation are not suggestive of particular migration routes to Iceland because they show similarities to both Eurasian and North American living and/or fossil taxa. For example, Tsuga comprises about nine living species in East Asia and North America. During the Tertiary, the genus was a common element in Europe and North America. A distinct type of Tsuga pollen occurs for the first time in the 9–8 Ma formation of Iceland. This pollen type is similar to the modern eastern North 7.5 Taxonomic Affinities and Origin of Newcomers 381 Fig. 7.6 Climate diagrams for modern Iceland, and for climate stations resembling the climatic conditions inferred for the middle Late Miocene of Iceland (climate diagrams from Lieth et al. 1999). 1. Vestmannaeyjar, Cfc climate. 2. Boston, Cfb climate. 3. Gothenburg, Cfb climate. 4. Klagenfurt, Dfb climate (climate types according to Köppen, cf. Kottek et al. 2006) 382 7 The Middle Late Miocene Floras (9–8 Ma) American species T. canadensis (L.) Carrière (Sivak 1978). Similar types of pollen have been recovered from Tertiary sediments in Europe from the Oligocene onwards (Sivak 1978). Hence, no distinct migration route to Iceland can be determined for this taxon. The leaves of Betula cristata from the Late Miocene of Iceland are comparable to another fossil taxon, B. pseudolumnifera Givul, a birch from the Late Miocene of southern and western Europe. The latter has been compared to the modern Japanese B. maximowicziana Regel (Kvaček et al. 2002). Similarities in leaf symmetry, leaf base, and dentition are also observed with the North American species B. lenta L. and B. papyrifera Marsh. According to Grímsson and Denk (2007) this taxon might have reached Iceland either from the west or from the east. Quercus sp. 1 either belongs to the modern white oaks or red oaks (infrageneric groups Quercus and Lobatae, according to Denk and Grimm 2009a, 2010). While the white oaks have a northern temperate distribution, red oaks are, at present, confined to North America. Since it cannot be determined whether this pollen represents red or white oaks, it remains unclear whether it colonized Iceland from the west or from the east (Denk et al. 2010). In contrast to the previous examples, a particular migration route to Iceland can be determined for Fagus gussonii. Fagus gussonii is a distinct Late Miocene species that has a geographical range in southern Europe and Iceland (Grímsson and Denk 2005). Although it is difficult to compare it to a particular modern species (Denk and Grimm 2009b), its Miocene distribution suggests that it migrated to Iceland from Europe. Generally, the first occurrence of oak pollen and of Fagus gussonii in the middle Late Miocene of Iceland strongly indicates that plants without long distance dispersal were still migrating to Iceland in this period. This in turn suggests that parts of the North Atlantic land bridge had remained subaerial until the Late Miocene (compare also Thiede and Eldholm 1983). 7.6 Comparison to Coeval northern Hemispheric Floras At the global and European scales, the time period 9–8 Ma appears not to have been characterized by dramatic shifts in climate or vegetation cover (Zachos et al. 2001; Mosbrugger et al. 2005). Northern hemispheric cooling continued gradually. In Iceland, various warmth-loving elements vanished between 10 and 9–8 Ma (e.g. Betula islandica [section Costatae], Parthenocissus, Platanus, Smilax). Similarly, the Homerian Stage (11.3–8 Ma) in northwestern Canada and Alaska was marked by a continuous cooling (White et al. 1997). The Grubstake flora (Alaska; Leopold and Liu 1994; Appendix 7.1) is fairly similar to the Icelandic middle Late Miocene floras. Conifers are quite diverse, including various types of Tsuga. Among the angiosperms, the number of temperate taxa is markedly low. Pterocarya occurs both in the floras of Iceland and in the Alaskan flora; Smilax and Tilia are present in the flora from Alaska but are absent in Iceland. In contrast, Fagus and Ilex are present in the Icelandic floras, while they are absent in the Grubstake flora. Herbaceous taxa play an important role both in the floras from Alaska and Iceland. 7.7 Summary 383 The Teewinot Formation, 8 Ma, central western USA (Barnosky 1984) is rather species-poor, containing a mixture of trees, shrubs, and herbaceous taxa. Among the Tertiary relicts are Pterocarya, Zelkova, and Carya, the records for which belong to the last ones in the Rocky Mountains. Riparian elements comprise herbaceous taxa and trees. The high percentage of Sarcobatus pollen found in this formation may indicate environmental conditions similar to today (BSk, steppe climate). The modern species S. vermiculatus (Hook.) Torr. is a halophytic shrub that occurs in western North America. Sarcobatus, Ephedra, and Juniperus, together with Ulmus and herbaceous taxa, may have inhabited drier microsites, while Pterocarya and Zelkova may have persisted in sheltered valleys (Appendix 7.1). Overall, this appears to reflect increased continentality in the Rocky Mountains in the middle Late Miocene. Older floras in western North America contain numerous elements typical of humid warm temperate vegetation types. At the same time, the extinction of humid temperate Tertiary relicts (Pterocarya, Zelkova) was nearly completed by 8 Ma (Barnosky 1984). In Southern Europe, the Makrilia flora (Crete, MN11, 8.6–7.7 Ma; Sachse and Mohr 1996; Sachse 2004) is a fairly rich flora in the southeastern Mediterranean region. This flora is markedly different from co-eval high latitude floras and has a clearly subtropical appearance. Elements such as Taxodium, Berberidaceae, Lauraceae, Illiciaceae, Nyssaceae, evergreen oaks of Quercus infrageneric group Ilex, Rutaceae, and Symplocaceae are frequently found in the Miocene of mid-latitudes and partly span a wide stratigraphic range (Mai 1995), but reached Iceland in only a few exceptional cases (Lauraceae in the 12 Ma formation of Iceland; Chap. 5). Nevertheless, a small subset of broadleaved deciduous taxa present in the Makrilia flora is also present in the Skarðsströnd-Mókollsdalur Formation. At the generic level, this applies to Acer, Ulmus, Carpinus, Fagus, Ilex, Pterocarya, and Salix among others. Among these, members of Acer and Carpinus in the Makrilia and Mókollsdalur floras may represent quite different lineages with distinctive ecologies. Others, such as Pterocarya and Fagus gussonii may have occupied similar niches in the Mediterranean and subarctic regions at the time of deposition. Fagus gussonii reaches the southeasternmost limit of its distribution range in the flora of Makrilia, whereas its northwesternmost limit is in Iceland. The stenoecious nature of Fagus (cf. Denk and Grimm 2009b), requiring fully humid or nearly so Cf (to Df) climate types, would suggest that this taxon thrived at higher elevations on Crete (or, alternatively, the climate in Crete was remarkably humid). Given a still weaker south-north temperature gradient than today, Fagus would have extended to Iceland, where it grew in moist, cool temperate conditions. 7.7 Summary The geological setting of the 9–8 Ma plant-bearing sedimentary rocks suggests that the plant assemblage recovered reflects regional vegetation in the vicinity of a caldera lake. The time period 9–8 Ma is characterized by impoverished broadleaved 384 7 The Middle Late Miocene Floras (9–8 Ma) deciduous forests. The dominant tree species were Fagus and possibly Quercus. From the Skarðsströnd-Mókollsdalur Formation, many insects have also been recovered, but they have not been studied properly with the single exception of a hickory aphid that has close biogeographic ties to eastern North America. Among plants, warmth-loving elements of the older 10 Ma formation have largely vanished. The Mókollsdalur biota shows small-scale vegetation differentiation (with slope exposure determining Fagus- versus Quercus-dominated forests) as seen in cool temperate northern hemisphere forests. Potential modern analogues of fossil taxa and vegetation types predominantly thrive under Cfb climates. Appendix 7.1 Floristic composition of the 9–8 Ma sedimentary formation of Iceland compared to contemporaneous northern hemispheric fossil assemblages at mid and high latitudes. Skarðsströnd-Mókollsdalur flora [ca 65º30´ n 21º31´ W] 9–8 Ma This study 1 Huperzia sp. 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1, 3 Lycopodiella sp. Lycopodium sp. Monolete spore, fam., gen. et spec. indet. 1 Monolete spore, fam., gen. et spec. indet. 2 Osmunda sp. Polypodiacceae gen. et spec. indet. 1 Polypodiaceae gen. et spec. indet. 6 Abies sp. Larix sp. Picea sect. Picea Pinus sp. 1 Pinus sp. 2 Pseudotsuga sp. Sciadopitys sp. Tsuga sp. 1 Tsuga sp. 2 Acer askelssonii 1, 3 1 1, 3 3 1 1 1–3 3 3 3 3 3 1–3 1 1 1 1–3 1 1 1 1, 3 1 1 1–3 Acer crenatifolium subsp. islandicum aff. Calycanthaceae Alnus cecropiifolia Angiosperm fam. et gen. indet. A Apiaceae gen. et spec. indet. 1 Asteraceae gen. et spec. indet. 1 Betula cristata cf. Carpinus Cornus sp. Cyclocarya sp. Dicotylophyllum sp. D Dicotylophyllum sp. E Fagus gussonii Ilex sp. 2 Myrica sp. Poaceae gen. et spec. indet. 1 Pterocarya sp. Quercus infrageneric group Quercus sp. 1 Ranunculaceae gen. et spec. indet. 2 Rhododendron sp. 2 Salix gruberi Tetracentron atlanticum Thalictrum sp. 2 Ulmus section Ulmus sp. Appendix 7.1 Teewinot flora, lower Gros Ventre River [ca 43º 35´ n 110º 21´ W] 8 Ma Barnosky, 1984 1 Abies sp. 1 Cupressaceae 1 Juniperus sp. 1 Picea sp. 1 Pinus sp. 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Ephedra sp. Artemisia sp. Carya sp. Chenopodiineae Cyperaceae Gilia sp. Gramineae [=Poaceae] Pterocarya sp. Salix sp. Sapindaceae sp. Sarcobatus sp. Sparganium sp. Tubuliflorae spp. [=Asteraceae] Ulmus / zelkova sp. 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Grubstake flora, Alaska [ca 64º n 148º 11´ e] 8 Ma Leopold & Liu, 1994; White et al., 1997 1 Cyathea sp. 1 Lycopodium cf. L. alopecuroides 1 Lycopodium cf. L. annotinum 1 Lycopodium cf. L. complanatum 1 Lycopodium cf. L. lucidulum 1 osmunda sp. 1 1 1 1 1 1 1 1 1 1 1 1 1 Selaginella sp. Abies cf. A. grandis Larix / Pseudotsuga sp. Picea sp. Pinus spp. Tsuga cf. T. canadensis Tsuga cf. T. heterophylla Tsuga cf. T. mertensiana Alnus cf. firma Alnus spp. Araliaceae Betula sp. Caprifoliaceae 1 385 ?Castanea / Castanopsis sp. – reworked grains Chenopodiaceae Chenopodiineae Corylus sp. Cyperaceae ?Diervilla / Weigela sp. ericales Gramineae [=Poaceae] Juglans sp. Juncus sp. ?Magnolia sp. – reworked grains Myrica sp. Onagraceae Polygonum persicaria Pterocarya sp. Ranunculaceae Rhododendron sp. Salix sp. Smilax sp. Sparganium sp. Tilia sp. Typha sp. Ulmus/zelkova sp. Viburnum sp. Makrilia flora, Crete [ca 35°03´ n 25°43´ e] 8.6–7.7 Ma Sachse & Mohr, 1996; Sachse, 2004 1 Abies sp. 1 Cathaya sp. 1 Cedrus sp. 1 Cupressaceae 1 Picea sp. 1, 2 Pinaceae 2 Pinidae 1, 3 Pinus cf. hampeana 1, 3 Pinus cf. hepios 1, 3 Pinus spp. 1, 3 Tetraclinis salicornoides 1, 3 Tetraclinis sp. 1, 3 Taxodium dubium 1 Tsuga sp. 1 Ephedra sp. 3 Acer decipiens 1, 2 Acer spp. (continued) 386 Makrilia flora (continued) 1, 2 aff. Ulmus sp. 2 Ailanthus vel Chenopodiaceae 1, 3 Alnus sp. 3 Ampelopsis vel Vitis 1 Apiaceae 1 Aquifoliaceae 1, 2 Aquilaria sp. 1 Araliaceae 1 Asteraceae 1 Asteroideae 3 Berberis/Mahonia sp. Brassiacaceae 1 1 Buxus cf. bahamensis 1, 3 Buxus cf. egeriana 1, 3 Buxus pliocenica 1, 3 Carpinu sp. 1, 2 Carpinus cf. orientalis 1, 2 Carya sp. 1 Caryophyllaceae 1 Celastraceae 1 Celastrus sp. 1 Celtis sp. 1 cf. Centaurea 1 Chenopodiaceae Cinnamomophyllum sp. 3 Cistus sp. 1 3 Cladastris sp. 1 Convolvulus spp. Cymodocea vel Posidonia 3 1, 3 Cyperaceae 1 cf. Cyrilla sp. 3 cf. Dalbergia sp. 1 Dipcadi sp. 1–3 Engelhardieae 1 Ericaceae vel Empetraceae 1, 3 Ericaceae vel Myrtaceae 1, 3 Fagus cf. attenuata 3 Fagus cf. gussonii 2 Fraxinus sp. 1 Hedera 1 Helianthemum sp. 2 Homalium vel Styracaceae 1, 3 Ilex cf. aquifolium 3 Illicium rhenanum 1 Juglans sp. 1 Lamiaceae 3 Laurophyllum spp. 7 The Middle Late Miocene Floras (9–8 Ma) 1 Leea sp. 1–3 Leguminosae spp. 2, 3 cf. Leguminosites spp. 1 1 1, 3 3 3 1 1 3 1 1, 3 1 3 1 1 1 1 3 3 1 1 1 2 1 1 1 1, 3 1, 3 1, 3 1, 2 1, 2 2 1 3 1, 3 1 1 1 3 1 3 3 1 1, 2 1 2 Liliaceae Linum spp. Lonicera cf. etrusca Machaerium spp. Magnolia sp. Microtropis cf. fallax Molospermum sp. Monocotyledonae Morus cf. nigra Myrica cf. lignitum Myristicaceae Myrtaceae Nypa Nyssaceae Oleaceae cf. Peristophe sp. Phillyrea sp. Pistacia cf. lentiscus Plantaginaceae Poaceae Polygonaceae Populus sp. Potamogeton cf. lucens Potamogeton sp. Pterocarya sp. Quercus cf. mediterranea Quercus kubinyi cf. Quercus rhenana Quercus spp. Ranunculaceae cf. Ruppia sp. Ruta/Dictamus sp. Salix cf. purpurea Salix spp. Sambucus sp. Sanguisorba sp. Sapotaceae cf. Smilax sp. Sparganiaceae Swartzia sp. Symplocos cf. minutula Symplocos sp. Tilia sp. Tiliaceae cf. Toddalia sp. (continued) References Makrilia flora (continued) 1 Typha sp. 387 3 Ulmus plurinerva 1 Zelkova davidii 1, 3 Zelkova zelkovaefolia Boldface indicates that genus is present in the Skarðsströnd-Mókollsdalur Formation. Grey shading indicates that genus is present in younger and older formations in Iceland. 1 based on pollen, spores; 2 based on leaves and/or fruit/seed fossils; 3 based on leaf fossils References Akhani, H., & Salimian, M. (2003). An extant disjunct stand of Pterocarya fraxinifolia (Juglandaceae) in the central Zagros Mountains, W Iran. Willdenowia, 33, 113–120. Akhmetiev, M. A., Bratzeva, G. M., Giterman, R. E., Golubeva, L. V., & Moiseyeva, A. I. (1978). Late Cainozoic stratigraphy and flora of Iceland. Transactions of the Academy of Sciences USSR 316, 1–188. Áskelsson, J. (1961). Um íslenzka steingervinga. In S. Þórarinsson (Ed.), Náttúra Íslands (pp. 47–63). Reykjavík: Almenna Bókafélagið. Bárðarson, G. G. (1918). Um surtarbrand. Andvari, 43, 1–71. Barnosky, C. W. (1984). Late Miocene vegetational and climatic variations inferred from the pollen record in Northwest Wyoming. Science, 232, 49–51. Camus, A. (1936-1938). Les Chênes. Monographie du genre Quercus. Tome I. Genre Quercus, sous-genre Cyclobalanopsis, sous-genre Euquercus (sections Cerris et Mesobalanus). Texte. Paris: Paul Lechevalier. 686 pp. Camus, A. (1938-1939). Les Chênes. Monographie du genre Quercus. Tome II. Genre Quercus, sous-genre Euquercus (sections Lepidobalanus et Macrobalanus). Texte. Paris: Paul Lechevalier. 830 pp. Camus, A. (1952-1954). Les Chênes. Monographie du genre Quercus. Tome III. Genre Quercus: sous-genre Euquercus (sections Protobalanus et Erythrobalanus) et genre Lithocarpus. Texte. Paris: Paul Lechevalier. 1314 pp. Denk, T., & Grimm, G. W. (2009a). Significance of pollen characteristics for infrageneric classification and phylogeny in Quercus (Fagaceae). International Journal of Plant Sciences, 170, 926–940. Denk, T., & Grimm, G. W. (2009b). The biogeographic history of beech trees. Review of Palaeobotany and Palynology, 158, 83–100. Denk, T., & Grimm, G. W. (2010). The oaks of western Eurasia: Traditional classifications and evidence from two nuclear markers. Taxon, 59, 351–366. Denk, T., Grímsson, F., & Kvaček, Z. (2005). The Miocene floras of Iceland and their significance for late Cainozoic North Atlantic biogeography. Botanical Journal of the Linnean Society, 149, 369–417. Denk, T., Grímsson, F., & Zetter, R. (2010). Episodic migration of oaks to Iceland: Evidence for a North Atlantic “land bridge” in the latest Miocene. American Journal of Botany, 97, 276–287. Ellenberg, H. (1986). Vegetation Mitteleuropas mit den Alpen. Stuttgart: Ulmer. 989 pp. Flora of China Editorial Committee. (1999). Flora of China, Cycadaceae through Fagacaeae (Vol. 4). St. Louis: Missouri Botanical Garden Press. 453 pp. Friedrich, W. L., & Símonarson, L. A. (1982). Acer-Funde aus dem Neogene von Island und ihre stratigraphische Stellung. Palaeontographica B, 182, 151–166. Friedrich, W. L., Símonarson, L. A., & Heie, O. E. (1972). Steingervingar í millilögum í Mókollsdal. Náttúrufræðingurinn, 42, 4–17. Grímsson, F., & Denk, T. (2005). Fagus from the Miocene of Iceland: Systematics and biogeographical considerations. Review of Palaeobotany and Palynology, 134, 27–54. 388 7 The Middle Late Miocene Floras (9–8 Ma) Grímsson, F., & Denk, T. (2007). Floristic turnover in Iceland from 15 to 6 Ma extracting biogeographical signals from fossil floral assemblages. Journal of Biogeography, 34, 1490–1504. Grímsson, F., & Símonarson, L. A. (2006). Beyki úr íslenskum setlögum. Náttúrufræðingurinn, 74, 81–102. Grímsson, F., Símonarson, L. A., & Friedrich, W. L. (2005). Kynlega stór aldin úr síðtertíerum setlögum á Íslandi. Náttúrufræðingurinn, 73, 15–29. Hegi, G. (1926). Illustrierte Flora von Mitteleuropa, part 1 (Vol. 5). Munich: J. F. Lehmanns Verlag. 674 pp. Heie, O. E., & Friedrich, W. L. (1971). A fossil specimen of the North American hickory aphid (Longistigma caryae Harris), found in Tertiary deposits in Iceland. Entomologica Scandinavica, 2, 74–80. Jensen, R. J. (1997). Quercus Linnaeus sect. Lobatae Loudon, Hort. Brit., 385. 1830. Red or black oaks. In Flora of North America Editorial Committee, (Ed.), Flora of North America North of Mexico, vol. 3. Magnoliophyta: Magnoliidae and Hamamelidae (pp. 447–468). New York: Oxford University Press. Jóhannesson, H., & Sæmundsson, K. (1989). Geological map of Iceland 1:500 000. Bedrock Geology. Reykjavík: Icelandic Museum of Natural History and Icelandic Geodetic Survey. Jóhannesson, H., & Sæmundsson, K. (1998). Geological map of Iceland 1:500 000. Tectonics. Reykjavík: Icelandic Institute of Natural History. Kottek, M., Grieser, J., Beck, C., Rudolf, B., & Rubel, F. (2006). World map of the Köppen-Geiger climate classification updated. Meteorologische Zeitschrift, 15, 259–263. Kvaček, Z., Velitzelos, D., & Velitzelos, E. (2002). Late Miocene flora of Vegora Macedonia N. Greece. Athens: Korali Publications. 175 pp. Landmælingar Íslands. (1994). Uppdráttur Íslands. Blað 35, Norðurárdalur. Scale 1:100000. Leopold, E. B., & Liu, G. (1994). A long pollen sequence of Neogene age, Alaska range. Quaternary International, 22(23), 103–140. Lieth, H., Berlekamp, J., Fuest, S., & Reidiger, S. (1999). Climate Diagram World Atlas (CD-Series: Climate and Biosphere). Leiden: Backhuys Publishers. Mai, H. D. (1995). Tertiäre Vegetationsgeschichte Europas. Jena: Gustav Fischer. 691 pp. McDougall, I., Kristjansson, L., & Saemundsson, K. (1984). Magnetostratigraphy and geochronology of Northwest Iceland. Journal of Geophysical Research, 89, 7029–7060. Mosbrugger, V., Utescher, T., & Dilcher, D. L. (2005). Cenozoic continental climatic evolution of Central Europe. Proceedings of the National Academy of Sciences of the United States of America, 102(42), 14964–14969. Nixon, K. C., & Muller, C. H. (1997). Quercus Linnaeus sect. Quercus. White oaks. In Flora of North America Editorial Committee (Ed.), Flora of North America north of Mexico, vol. 3. Magnoliophyta: Magnoliidae and Hamamelidae (pp. 471–506). New York: Oxford University Press. Sachse, M. (2004). Die neogene Mega- und Mikroflora von Makrilia auf Kreta und ihre Aussagen zur Klima- und Vegetationsgeschichte des östlichen Mittelmeergebietes. Flora Tertiaria Mediterranea, 12, 1–254. Sachse, M., & Mohr, B. A. R. (1996). Eine obermiozäne Makro- und Mikroflora aus Südkreta (Griechenland), und deren paläoklimatische Interpretation – Vorläufige Bemerkungen. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, 200, 149–182. Schwarzbach, M. (1955). Beiträge zur Klimageschichte Islands 1. Allgemeiner Überblick der Klimageschichte Islands. Neues Jahrbuch für Geologie und Paläontologie Monatsheft, 3, 97–130. Símonarson, L. A. (1981). Íslenskir steingervingar. In Þórarinsson, S. (Ed.), Náttúra Íslands (2nd ed., pp. 157–173). Reykjavík: Almenna bókafélagið. Símonarson, L. A., & Friedrich, W. L. (1983). Hlynblöð og hlynaldin í íslenskum jarðlögum. Náttúrufræðingurinn, 52, 156–174. Sivak, J. (1978). Histoire du genre Tsuga en Europe. D’aprés l’étude des grains de pollen actuels et fossiles. Paleobiologie Continentale, 9(1), 1–226. Thiede, J., & Eldholm, O. (1983). Speculations about the paleodepth of the Greenland-Scotland Ridge during late Mesozoic and Cenozoic times. In M. H. P. Bott, S. Saxow, M. Talwani, & Explanation of Plates 389 J. Thiede (Eds.), Structure and development of the Greenland-Scotland Ridge: New methods and concepts (pp. 445–456). New York: Plenum. Thompson, R. S., Anderson, K. H., & Bartlein, P. J. (1999). Atlas of relations between climatic parameters and distribution of important trees and shrubs in North America-Hardwoods. U.S. Geological Survey Professional Paper, 1650-B, 1–423. Thoroddsen, Þ. (1896). Nogle iagttagelser over surtarbrandesn geologiske forhold i det nordvestlige Island. Geologiska Föreningens i Stockholm Förhandlingar, 18, 114–154. Utescher, T., & Mosbrugger, V. (2009). Palaeoflora Database. http://www.geologie.unibonn.de/ Palaeoflora van Gelderen, D. M., de Jong, P. C., & Oterdoom, H. J. (1994). Maples of the World. Portland: Timber Press. 458 pp. White, J. M., Ager, T. A., Adam, D. P., Leopold, E. B., Giu, G., Jetté, H., & Schweger, C. E. (1997). An 18 million year record of vegetation and climate change in northwestern Canada and Alaska: tectonic and global climatic correlates. Palaeogeography, Palaeoclimatology, Palaeoecology, 130, 293–306. Zachos, J. C., Pagani, M., Sloan, L., Thomas, E., & Billups, K. (2001). Trends, rhythms, and aberrations in global climate 65 Ma to present. Science, 292, 686–693. explanation of Plates Plate 7.1 1. Hrútagil in Mókollsdalur, northwestern Iceland, Skarðsströnd-Mókollsdalur Formation (ca 8 Ma). Stream running down the Hrútagil gully, outcrop with fossils in middle of photo, Mókollsdalur valley seen in the background. 2. View up the gully Hrútagil from Mókollsdalur valley. 3–7. Variation in preservation of plant fossils and sedimentary rock type (diatomite, siltstone, sandstone). Most fossils are preserved as compressions with some organic material on both part and counterpart, but some only as impressions Plate 7.2 1–3. Lycopodiella sp. 1. Spore in SEM, proximal polar view showing trilete tetrad mark. 2. Detail of spore surface. 3. Spore in LM, proximal polar view showing trilete tetrad mark. 4–6. Lycopodiella sp. 4. Spore in SEM, proximal polar view. 5. Detail of spore surface. 6. Spore in LM, distal polar view. 7–9. Lycopodium sp. 7. Spore in SEM. 8. Detail of spore surface. 9. Spore in LM. 10–12. Lycopodium sp. 10. Spore in SEM, distal polar view. 11. Detail of spore surface. 12. Spore in LM, polar view Plate 7.3 1–3. Huperzia sp. 1. Spore in SEM, distal polar view. 2. Detail of spore surface. 3. Spore in LM, proximal polar view showing trilete tetrad mark. 4–6. Osmunda sp. 4. Spore in SEM, oblique polar view. 5. Detail of spore surface. 6. Spore in LM, oblique polar view. 7–9. Osmunda sp. 7. Spore in SEM. 8. Detail of spore surface. 9. Spore in LM. 10–12. Polypodiaceae gen. et spec. indet. 1. 10. Monolete spore in SEM, equatorial view. 11. Detail of spore surface. 12. Spore in LM, equatorial view Plate 7.4 1–3. Polypodiaceae gen. et spec. indet. 6. 1. Spore in SEM, distal polar view. 2. Detail of spore surface. 3. Spore in LM, polar view. 4–6. Monolete spore fam. gen. et spec. indet. 1. 4. Spore in SEM, proximal polar view showing monolete tetrad mark. 5. Detail of spore surface. 6. Spore in LM. 7–9. Monolete spore fam. gen. et spec. indet. 2. 7. Spore in SEM, proximal polar view showing monolete tetrad mark. 8. Detail of spore surface. 9. Spore in LM, oblique polar view. 10–12. Monolete spore fam. gen. et spec. indet. 2. 10. Spore in SEM, distal polar view. 11. Detail of spore surface. 12. Spore in LM, proximal polar view showing monolete tetrad mark 390 7 The Middle Late Miocene Floras (9–8 Ma) Plate 7.5 1–3. Larix/Pseudotsuga sp. 1. Pollen grain in SEM. 2. Detail of pollen grain surface. 3. Pollen grain in LM. 4. Picea sp., winged seed (IMNH org 147). 5–7. Picea sp. 5. Bisaccate pollen grain in SEM, equatorial view. 6. Detail of cappa surface. 7. Bisaccate pollen grain in LM, equatorial view. 8–11. Pinus sp. 2 (Diploxylon type). 8. Bisaccate pollen grain in SEM, equatorial view. 9. Detail of cappa surface. 10. Bisaccate pollen grain in LM, polar view. 11. Bisaccate pollen grain in LM, equatorial view Plate 7.6 1–3. Pinus sp. 2 (Haploxylon type). 1. Bisaccate pollen grain in SEM, equatorial view. 2. Detail of cappa surface. 3. Bisaccate pollen grain in LM, equatorial view. 4–6. Larix/ Pseudotsuga sp. 4. Pollen grain in SEM. 5. Detail of pollen grain surface. 6. Pollen grain in LM. 7–9. Sciadopitys sp. 7. Pollen grain in SEM, distal polar view. 8. Detail of pollen grain surface. 9. Pollen grain in LM Plate 7.7 1–4. Tsuga sp.1 1. Monosaccate pollen grain in SEM, distal polar view. 2. Monosaccate pollen grain in LM, distal polar view. 3. Detail of saccus. 4. Detail of corpus. 5–8. Tsuga sp. 2. 5. Monosaccate pollen grain in SEM, distal polar view. 6. Monosaccate pollen grain in LM, distal polar view. 7. Detail of saccus. 8. Detail of corpus Plate 7.8 1–3. Apiaceae gen. et spec. indet. 5. 1. Pollen grain in SEM, equatorial view. 2. Detail of pollen grain surface. 3. Pollen grain in LM, equatorial view. 4–6. Apiaceae gen. et spec. indet. 1. 4. Pollen grain in SEM, equatorial view. 5. Detail of pollen grain surface. 6. Pollen grain in LM, equatorial view. 7–9. Ilex sp. 2. 7. Pollen grain in SEM, equatorial view. 8. Detail of pollen grain surface. 9. Pollen grain in LM, equatorial view. 10–12. Asteraceae gen. et spec. indet. 1. 10. Pollen grain in SEM, polar view. 11. Detail of pollen grain surface. 12. Pollen grain in LM, polar view Plate 7.9 1. Alnus cecropiifolia, large wide elliptic leaf (IMNH). 2. Detail of Fig. 1 showing tertiary venation and teeth along margin. 3. Alnus cecropiifolia, large elliptic leaf (IMNH). 4. Alnus kefersteinii, female infructescences (IMNH). 5. Alnus kefersteinii, female infructescences (IMNH). 6. Alnus/Betula sp., male catkins (IMNH). 7–9. Alnus sp. 1. 7. Detail of pollen grain surface. 8. Pollen grain in SEM, polar view. 9. Pollen grain in LM, polar view Plate 7.10 1. Betula cristata, large ovate leaf (IMNH). 2. Betula cristata, large ovate leaf (IMNH). 3. Betula cristata, catkin scale (IMNH). 4. Betula cristata, small narrow elliptic leaf. 5–7. Betula sp. 5. Pollen grain in SEM, polar view. 6. Detail of pollen grain surface. 7. Pollen grain in LM, polar view Plate 7.11 1. cf. Carpinus sp., narrow elliptic leaf with cordate base, numerous small teeth along margin (IMNH org 149). 2. Cornus sp., wide elliptic leaf, entire margined (IMNH). 3–5. aff. Calycanthaceae 3. Pollen grain in SEM, equatorial view. 4. Detail of pollen grain surface. 5. Pollen grain in LM, equatorial view Plate 7.12 1–4. Rhododendron sp. 2. 1. Tetrad in SEM. 2. Tetrad in LM. 3. Detail of tetrad surface close to apertures. 4. Detail of tetrad surface in mesocolpium. 5–7. Fagus sp. (F. gussonii). 5. Pollen grain in SEM, oblique equatorial view. 6. Detail of pollen grain surface. 7. Pollen grain in LM, oblique equatorial view. 8–10. Fagus sp. (F. gussonii). 8. Pollen grain in SEM, polar view. 9. Detail of pollen grain surface. 10. Pollen grain in LM, polar view Plate 7.13 1–4. Fagus gussonii. 1. Medium sized leaf with oblong base with obtuse very-base (IMNH). 2. Part of leaf, medium sized wide elliptic. 3. Medium sized elliptic leaf with dentate margin and acuminate apex (IMNH). 4. Large elliptic leaf with obtuse base, weakly dentate margin (IMNH) Explanation of Plates 391 Plate 7.14 1–10. Fagus gussonii. 1. Medium sized elliptic leaf with obtuse base and craspedodromous venation (IMNH). 2. Small leaf with dentate margin (IMNH). 3. Cupule with a long peduncle (IMNH). 4. Cupule with part of peduncle (IMNH). 5. Cupule with traces of spine-like appendages (IMNH). 6. Bud scale (IMNH). 7. Bud scale (IMNH). 8. Bud scale (IMNH). 9. Winged nut (IMNH). 10. Winged nut (IMNH). 11–13. Quercus infrageneric group Quercus sp. 1. 11. Pollen grain in SEM, equatorial view. 12. Detail of pollen grain surface. 13. Pollen grain in LM, equatorial view Plate 7.15 1. Pterocarya sp., compound leaf (IMNH org 72). 2. Pterocarya sp., large leaflet (IMNH). 3. Pterocarya sp., nutlet with two lateral wings (IMNH org 73). 4. Detail of Fig. 2 showing teeth along margin. 5. Detail of Fig. 2 showing asymmetric base. 6. Cyclocarya sp., large leaflet (IMNH) Plate 7.16 1–3. Pterocarya sp. 1. Pollen grain in SEM, polar view. 2. Detail of pollen grain surface. 3. Pollen grain in LM, polar view. 4–6. Pterocarya sp. 4. Pollen grain in SEM, polar view. 5. Detail of pollen grain surface. 6. Pollen grain in LM, polar view. 7–9. Myrica sp. 7. Pollen grain in SEM, polar view. 8. Detail of pollen grain surface. 9. Pollen grain in LM, polar view. 10–12. Myrica sp. 10. Pollen grain in SEM, polar view. 11. Detail of pollen grain surface. 12. Pollen in LM, polar view Plate 7.17 1–3. Poaceae gen. et spec. indet. 1. 2. Pollen grain in SEM. 2. Detail of pollen grain surface. 3. Pollen grain in LM. 4–6. Thalictrum sp. 2. 4. Pollen grain in SEM. 5. Detail of pollen grain surface. 6. Pollen grain in LM. 7–9. Ranunculaceae gen. et spec. indet. 2. 7. Pollen grain in SEM, equatorial view. 8. Detail of pollen grain surface. 9. Pollen grain in LM, equatorial view. 10–12. Ranunculaceae gen. et spec. indet. 2. 10. Pollen grain in SEM, equatorial view. 11. Detail of pollen grain surface. 12. Pollen grain in LM, equatorial view Plate 7.18 1. Salix gruberi, part of leaf (IMNH). 2. Acer askelssonii, large 7 lobed leaf (IMNH). 3. Acer askelssonii, large 5 lobed leaf (IMNH) Plate 7.19 1. Acer crenatifolium subsp. islandicum, small narrow 3 lobed leaf (IMNH). 2. Acer crenatifolium subsp. islandicum, medium sized 3 lobed leaf (IMNH). 3. Detail of Fig. 2 showing venation between lobes Plate 7.20 1–3. Acer sp.1. 1. Pollen grain in SEM, equatorial view. 2. Detail of pollen grain surface. 3. Pollen grain in LM, equatorial view. 4–6. Acer sp.1. 4. Pollen grain in SEM, equatorial view. 5. Detail of pollen grain surface. 6. Pollen grain in LM, equatorial view. 7–9. Acer sp. 1. 7. Pollen grain in SEM, equatorial view. 8. Detail of pollen grain surface. 9. Pollen grain in LM, equatorial view. 10–12. Acer sp. 2. Pollen grain in SEM, equatorial view. 11. Detail of pollen grain surface. 12. Pollen grain in LM, equatorial view Plate 7.21 1–3. Tetracentron atlanticum. 1. Pollen grain in SEM, polar view. 2. Detail of pollen grain surface. 3. Pollen grain in LM, polar view. 4–6. Tetracentron atlanticum. 4. Pollen grain in SEM, equatorial view. 5. Detail of pollen grain surface. 6. Pollen grain in LM, equatorial view. 7–9. Ulmus sp. 7. Pollen grain in SEM, oblique view. 8. Detail of pollen grain surface. 9. Pollen grain in LM, polar view. 10–12. Ulmus sp. 10. Pollen grain in SEM, polar view. 11. Detail of pollen grain surface. 12. Pollen grain in LM, polar view Plate 7.22 1. Ulmus sp. MT 2, medium sized elliptic leaf (IMNH 4742-02). 2. Ulmus sp. MT 2, small elliptic leaf (IMNH 4742-01). 3. Ulmus section Ulmus sp., samara, endocarp with wing (IMNH). 4. Detail of Fig. 3 showing apical notch of wing Plate 7.23 1–4. Angiosperm fam. gen. et spec. indet A. 5. Dicotylophyllum sp. D, seedling with leaves (IMNH 5561). 6. Dicotylophyllum sp. E, leaf or leaflet (IMNH) Plates Plate 7.1 Plates 393 Plate 7.2 394 7 The Middle Late Miocene Floras (9–8 Ma) Plate 7.3 Plates 395 Plate 7.4 396 7 The Middle Late Miocene Floras (9–8 Ma) Plate 7.5 Plates 397 Plate 7.6 398 7 The Middle Late Miocene Floras (9–8 Ma) Plate 7.7 Plates 399 Plate 7.8 400 7 The Middle Late Miocene Floras (9–8 Ma) Plate 7.9 Plates 401 Plate 7.10 402 7 The Middle Late Miocene Floras (9–8 Ma) Plate 7.11 Plates 403 Plate 7.12 404 7 The Middle Late Miocene Floras (9–8 Ma) Plate 7.13 Plates 405 Plate 7.14 406 7 The Middle Late Miocene Floras (9–8 Ma) Plate 7.15 Plates 407 Plate 7.16 408 7 The Middle Late Miocene Floras (9–8 Ma) Plate 7.17 Plates 409 Plate 7.18 410 7 The Middle Late Miocene Floras (9–8 Ma) Plate 7.19 Plates 411 Plate 7.20 412 7 The Middle Late Miocene Floras (9–8 Ma) Plate 7.21 Plates 413 Plate 7.22 414 7 The Middle Late Miocene Floras (9–8 Ma) Plate 7.23