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The Kap København Formation is a succession of clay, silt and sand in eastern North Greenland. The formation was discovered in 1979 and the sequence has been the focus of several subsequent visits (Funder and Hjort 1980). This short review on the Kap København Formation and its flora and fauna is based on Funder et al. (1984, 1985, 2001), Bennike (1990), Böcher (1995) and Símonarson et al. (1998).

The formation covers an area of ~300 km² and is exposed at numerous places along rivers. It has been divided into members A and B. Member A is at least 50 m thick and is dominated by finely laminated clay and silt with rare stones. This member contains rare shells of bivalves and more frequent tests of foraminifers and valves of ostracods. Member B is 40–50 m thick and is dominated by two sandy units (units B1 and B2), which are separated by a more fine‐grained unit (B2). B1 is dominated by horizontally laminated fine and medium grained sand, but cross bedding and other types of sedimentary structures also occur. The sand is texturally and mineralogically mature quartz sand with heavy mineral concentrations in some places. In the upper part large scour‐and‐fill structures are found, these contain large amounts of organic detritus. The sediments in unit B1 were deposited in coastal environments during rising water depth. Unit B2 is characterized by bioturbated clay and silt that was deposited on the inner shelf. Unit B3 is heterogeneous, but it is dominated by horizontally laminated sand. Logs of small trees (Figure 5a, see Plate section) as well as lenses and layers of organic detritus (Figure 5b) is a characteristic feature for unit B3, which is interpreted as deposited in coastal parts of delta environments. In the western part of the Kap København area unit B2 is missing and unit B3 is devoid of plant and animal remains. Member B in this area is interpreted as fluvial.

Member A and unit B2 contain relatively rich marine faunas. Member A contains an element of warmth demanding Foraminifera species. Unit B2 has a fairly diverse mollusc fauna that includes the bivalves Cyrtodaria kurriana and Macoma balthica, in addition to rich faunas of foraminifers and ostracods. The highest sea water temperatures probably prevailed during deposition of unit B2, with summer temperatures at the sea bottom 7–8 °C higher than at present. Both members A and B show sign of lowered salinity and influence from freshwater. On the surface of member A exposures strongly abraded shell fragments are rather common. They have been designated the allochthonous fauna; it comprises the bivalve Arctica islandica. The allochthonous fauna is assumed to be older than member A, and A. islandica is one of the most warmth‐demanding mollusc species found in the area.

Unit B1 and especially B3 contain a wealth of well‐preserved remains of non‐marine plants and animals, with many different groups represented. Vascular plants include a mixture of boreal and arctic species (Figure 6). Taxa such as Larix groenlandii, Picea mariana, Thuja occidentalis and Taxus sp., Betula sect. Albae, Myrica arctogale, Cornus stolonifera, Viburnum cf. edule and Scirpus microcarpus belong to the first group, whereas D. octopetala, O. digyna and Papaver sect. Scapiflora belong to the second. All remains of wood come from small trees or shrubs, and the largest log that was found had a diameter of 18 cm. Growth rings are narrow to extremely narrow, which may indicate that the mean temperature for the warmest month of the year was ~10–11 °C. Thuja and Taxus cannot tolerate very cold winters, and the mean temperature for the coldest month was probably not below −17 °C. Thus, it appears that the area was dominated by forest tundra, which grew in an oceanic type of sub‐arctic climate.

Figure 5 (a) A log of Larix sitting in sandy deposits of the Kap København Formation (member B) in North Greenland. The light part has been bleached by the sun. Note the contrasting modern treeless landscape. (b) Organic‐rich layers of the Kap København Formation (member B). (c) Excavation of last interglacial deposits on Jameson Land, central East Greenland. (d) Sandy interglacial deposits on Jameson Land with organic‐rich sediments in the bottom of a trough. (e) Archaeological excavation of a Mid‐Holocene midden in central West Greenland.

Figure 6 Drawings of plant remains from the Kap København Formation in North Greenland. (a‐b) Leaves of Dryas octopetala. Leaf that comes from a plant that grew on a protected site (a) and a narrow leaf with recurved leaf margin, which comes from a plant that grew on a wind‐exposed site (b). (c, d) Leaves of Betula nana. (e) Fruit stone of Cornus stolonifera. (f) Cone of Larix groenlandii. (g) Twig of Thuja occidentalis with three small cones. (h) Twig of Thuja occidentalis with scaly leaves. Thick scale bars: 10 mm, thin bars: 5 mm.

Source: From Bennike (1990).

By far the most diverse group of invertebrates is beetles, of which at least 210 species are present, an impressive and surprising number when compared with the modern day beetle fauna of Greenland that comprises ~36 species (Böcher 1988, 2012). The fossil insect fauna comprise 155 named species, of which 142 species are Coleoptera, mostly Carabidae, Staphylinidae, and Curculionidae. Ants are absent from modern Greenland, so it is remarkable that four species of ants (Formica and Camponotus) are represented in the Kap København fauna. Trichoptera (caddis flies) include nine named species and 12 genera, indicating the existence of a great variety of freshwater biotopes, which is confirmed by the presence of various chironomids, water beetles, macro‐limnophytes, crustaceans and bryozoans. Some examples of insect remains from the Kap København Formation are shown in Figure 7.

The insect fauna of the Kap København Formation allows a detailed palaeoecological reconstruction of a highly diverse environment. Freshwater, freshwater shores, humid terrestrial biotopes, forests and alpine biotopes each contributes about equal numbers of species, with somewhat fewer taxa from dry environments, including steppe and saline ponds (Böcher 1995).

Figure 7 Scanning electron microscope photographs of beetle and ant remains from the Kap København Formation in North Greenland. (a) Head of Cicindela cf. hybrida. (b‐d) Elytra of Aegialia terminalis, Scolytus piceae and Kalissus nitidus. (e) Head of Formica sp. (f) Elytron of Litodactylus leucogaster. Scale bars: 0.5 mm.

Source: From Böcher (1995).

Biogeographically the Kap København fossil flora is dominated by taxa with a modern Holarctic or Nearctic range (Figure 8, see Plate section; Bennike 1990), whereas the fossil insect fauna has an equal share of what are today Nearctic and Palaearctic elements (Böcher 1995). Nine of the beetles from the Kap København Formation are found in Greenland today; most of these are widespread Holarctic, low arctic–subarctic species such as the boreo‐alpine carabid N. rufescens. The greater part of the insects points to temperate conditions, but heterogeneous compositions of some of the insect assemblages indicate either subarctic or temperate summer temperatures (Böcher 1995).

Figure 8 Maps of the northern parts of the Earth, showing present geographical ranges of Picea mariana (a), Thuja occidentalis (b) and Cornus stolonifera (c). Remains of these species have been found in the Kap København Formation (black dot in North Greenland).

Source: From Bennike (1990).

Except in a few cases – the carabid Diacheila matthewsi (Böcher 1995) and a couple of undescribed staphylinids, which probably represent extinct species – all the named insect taxa have been referred to living species. Thus once more the longevity of insect species is demonstrated (Coope 1970, 1978, 1979; Buckland and Coope 1991). A few of the vascular plant remains are referred to extinct species: L. groenlandii, M. arctogale and Aracites globosa (Figure 9). The latter is an enigmatic species that may belong to the family Araceae (Aalto et al. 1992).

Figure 9 Scanning electron microscope photographs of fruits from extinct plants from the Kap København Formation in North Greenland. (a) Myrica arctogale. (b) Aracites globosa. Scale bars: 1 mm.

Source: From Bennike (1990).

The insect fauna and the flora of the Kap København Formation show a high degree of similarity with that from the 0.5–1 million years older Beaufort Formation on Meighen Island, Arctic Canadian Archipelago (Matthews, 1977, 1979a, 1979b; Matthews and Telka 1977; Matthews and Fyles 2000; Elias and Matthews 2002; Elias et al. 2006). For instance, at both sites the genus Bembidion and the subgenus Cryobius of Pterostichus (Carabidae) are predominant. There are, however, important differences as well. For instance, the genus Carabus is represented by several species on Meighen Island but not found in the Kap København sediments. These, in return, contain a species of Cicindela, a genus not represented in the Beaufort Formation. A strange absence in the Kap København Formation is that of Amara alpina, so common both in last interglacial sites from Greenland and in the Beaufort Formation (Matthews and Fyles 2000; Elias and Matthews 2002).

The dating of the Kap København Formation is based on a number of different methods, of which the most important are biostratigraphy, palaeomagnetic analyses and amino acid analyses. The biostratigraphically most important groups are foraminifers, ostracods, molluscs and mammals. The occurrence of the extinct rabbit Hypolagus sp. and the extant hare Lepus sp. in member B3 is particularly important. These genera co‐occurred in North America during the time period from ~2.3 to 2.0 million years BP (Repenning et al. 1987). This is in good agreement with the latest age estimate based on benthic foraminifera, which indicate an age for member B of ~2 Ma (Bennike et al. 2010), perhaps corresponding to marine isotope stage 77 and one of the so‐called super interglacials that have been documented in Arctic Russia (Melles et al. 2012).