Submarine Lateglacial lake deposits from the Kattegat, southern Scandinavia PETER WIBERG-LARSEN, 1 OLE BENNIKE 2 * and JØRN BO JENSEN 2 1 Institute for Bioscience, Aarhus University, Silkeborg, Denmark 2 Geological Survey of Denmark and Greenland (GEUS), Aarhus, Denmark Received 12 October 2018; Revised 4 January 2019; Accepted 20 January 2019 ABSTRACT: Lateglacial submarine lake sediments are reported for the first time from the Kattegat Sea in southern Scandinavia. The Lateglacial sediments were collected from a vibrocore that contained, from top to bottom, Holocene marine muddy sand, Holocene brackish-water mud, Early Holocene peat with remains of Betula pubescens and telmatic plants, Lateglacial lake deposits that are the focus of this paper, and homogenous sand. Radiocarbon dating of terrestrial plant remains from the Lateglacial sediments gave ages between 12 400 and 12 800 cal a bp, corresponding to the Younger Dryas. The Lateglacial sediments contain remains of Betula nana and other plants indicating a tundra-like open landscape with dwarf shrub heaths, which is typical for the region. Remains of macrolimnophytes indicate shallow carbonate-rich, cool lake waters. Remains of larvae of Trichoptera and Chironomidae dominate the invertebrate fauna and indicate a fairly species-rich fauna. Half of the trichopteran taxa today have their distribution north of Denmark or show a generally northern distribution in Europe. The lake sediments are found at  24 m below sea level, and the presence of lake sediments shows that this part of Kattegat had not been transgressed by the sea during the Younger Dryas. # 2019 John Wiley & Sons, Ltd. KEYWORDS: Chironomidae; Kattegat; Lateglacial; Quaternary; Trichoptera. Introduction In the late 1970s, the Danish State began to map deposits of sand and gravel in Danish waters. In 1984, a survey was carried out in southern Kattegat and several possible aggre- gate deposits were identified (Andersen et al., 1984), which were later called speculative resources. In 2016, vibrocoring was undertaken to check if the existence of these resources could be confirmed. One of the areas mapped in 1984, designated area 5, was described from interpretation of seismic data as an area with till covered by Holocene marine sand and gravel. No samples were collected in 1984 to check the interpretation, but in 2016 a vibrocore was collected from area 5. The core contained a succession of Lateglacial lake sediments, which proved to be unusually rich in remains of insect larvae, in particular Trichoptera (caddisflies) and Chironomidae (non-biting midges). Hence we decided to conduct a detailed study of invertebrate remains. The Kattegat is a sea area between Skagerrak and the Danish/Swedish straits (Fig. 1). Large parts in the south and west are shallow, with water depths of 5–20 m, whereas in the eastern and northern parts water depths of more than 100 m are found. Lateglacial marine deposits are widespread in the deeper parts of the Kattegat, as raised deposits in northern Jutland and along the west coast of Sweden (M€ orner, 1969). The Lateglacial marine fauna includes extralimital cold-adapted species such as the bivalve Portlandia arctica and mammals such as ringed seal Pusa hispida, bearded seal Erignathus barbatus and polar bear Ursus maritimus (Fred en, 1975; Berglund et al., 1992; Jensen et al., 2002a)  species that are mainly found in arctic regions today. In many palaeogeographical reconstructions, the shallow southern and western parts of the Kattegat are shown as land during the Lateglacial (Jensen et al., 1997, 2002b; Lambeck, 1999). However, until now no Lateglacial non- marine deposits with plant or animal remains have been reported from the Kattegat (M€ orner, 1969; Bennike et al., 2000; Jensen et al., 2002a; Bendixen et al., 2017). The aim of this paper is to discuss the palaeoecological, palaeoclimatic and palaeogeographical implications of the Lateglacial fauna and flora. Studies of invertebrate remains in lake deposits have a long tradition (Wesenberg-Lund, 1896) and almost all groups of invertebrates may leave remains in sediments (Frey, 1964). Johansen (1904) was one of the first to use invertebrate remains from Quaternary lake sediments for palaeoclimatic reconstructions, but his pioneering work was much criticized and debated (Johansen et al., 1906). However, Johansen concluded that the mean July temperature in Denmark during the Younger Dryas was about 8–12 ˚C, which is similar to more recent estimates. Hence, Iversen (1954) suggested from plant remains that the mean July temperature in Denmark was approximately 10 ˚C, when at its minimum, and Coope et al. (1998) suggested July temperatures of 8–10 ˚C for Scania in southern Sweden, based on beetle remains. Head capsules of chironomid larvae are now routinely used to infer palae- oclimate (Brooks et al., 2007; Heiri et al., 2014), placing mean July temperature in the Baltic region within the range of 11–12 ˚C during the Younger Dryas (Heiri et al., 2014). Remains of Trichoptera larvae are rarely included in palae- oclimatic studies of lake sediments, although the order is among the most species-rich in freshwater habitats. However, there are examples of their potential to characterize former running-water habitats (e.g. Wiberg-Larsen et al., 2001; Greenwood et al., 2003, 2006; Howard et al., 2009). Material and methods Sediment coring was carried out with a 10-cm-diameter vibrocorer with a 6-m-long PVC tube in a steel tube from the vessel Skoven. The coring location was selected from seismic data acquired in 1984 with the aim to map aggregates.  Correspondence: Ole Bennike, as above. E-mail: obe@geus.dk # 2019 John Wiley & Sons, Ltd. JOURNAL OF QUATERNARY SCIENCE (2019) 34(2) 165–171 ISSN 0267-8179. DOI: 10.1002/jqs.3089