Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo A multi-proxy palaeolimnological record of the last 16,600 years from coastal Lake Kushu in northern Japan Mareike Schmidt a, ⁎ , Christian Leipe a,b , Fabian Becker c , Tomasz Goslar d,e , Philipp Hoelzmann c , Jens Mingram f , Stefanie Müller g , Rik Tjallingii f , Mayke Wagner g , Pavel E. Tarasov a, ⁎ a Institute of Geological Sciences, Paleontology, Freie Universität Berlin, Malteserstr. 74-100, 12249 Berlin, Germany b Nagoya University, Institute for Space-Earth Environmental Research (ISEE), Research Institutes Building II, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan c Institute of Geographical Sciences, Physical Geography, Freie Universität Berlin, Malteserstr. 74-100, 12249 Berlin, Germany d Faculty of Physics, Adam Mickiewicz University, Umultowska, 85, Poznan, Poland e Poznan Radiocarbon Laboratory, Foundation of the A. Mickiewicz University, Rubiez 46, Poznan, Poland f Helmholtz Centre Potsdam, GeoForschungsZentrum, Telegrafenberg, 14473 Potsdam, Germany g Eurasia Department and Beijing Branch Office, German Archaeological Institute, Im Dol 2-6, 14195 Berlin, Germany ARTICLE INFO Keywords: Diatoms X-ray fuorescence Non-pollen palynomorphs Microfacies Holocene Optimum Hunter-gatherer occupation ABSTRACT Based on diatom, aquatic pollen and non-pollen palynomorph (NPP), lake sediment microfacies, and X-ray fuorescence (XRF) analyses we defne three main phases of lake basin development including a marshy phase (ca. 16,600–9400 cal. yr BP), lagoon phase (ca. 9400–5900 cal. yr BP) and freshwater lake phase (since ca. 5900 cal. yr BP). Marine infuence on the lake system linked to global sea-level rise and the Holocene marine transgression reached a maximum between ca. 8000 and 6000 cal. yr BP. An increase of Aulacoseira subarctica at 5530 cal. yr BP marks the end of the Holocene Thermal Optimum (i.e. onset of Middle Holocene cooling) in the study region. Our results further suggest that freshwater Lake Kushu had a signifcant efect on the initial ha- bitation of Rebun Island by sedentary hunter-gatherer populations. The reconstructed onset of stable freshwater conditions (ca. 5100 cal. yr BP) coincided with the appearance of the earliest permanent settlements during the Middle Jomon culture phase (ca. 5000–4000 cal. yr BP). On the other hand, there is evidence for human-induced changes in the limnological conditions. This includes enhanced sediment and nutrient input into Lake Kushu resulting in high eutrophication levels that caused strongly reduced diatom productivity and enhanced green algae growth, which can be attributed to human activities apparently associated with the Okhotsk (ca. 1450–950 cal. yr BP) and Classic Ainu (ca. 350–100 cal. yr BP) culture periods. 1. Introduction The sediment core RK12 from Lake Kushu on Rebun Island (Fig. 1) analyzed in the current study was obtained under the framework of the Baikal-Hokkaido Archaeology Project (BHAP: http://bhap.artsrn. ualberta.ca/). This international multi-disciplinary research initiative aims at investigating Holocene hunter-gatherer culture dynamics, variability, and resilience and their causal driving factors including possible relations to climate and environmental changes in two regions of the world: Lake Baikal in Russian Siberia and Hokkaido in northern Japan (Tarasov et al., 2013; Weber et al., 2013). Rebun Island in the northern Sea of Japan has been chosen as one of the key study areas in the latter region. First palaeoenvironmental studies (Kumano et al., 1990; Sato et al., 1998) on the Lake Kushu basin were based on a sediment core extracted from the mire in the River Oshonnai delta south of contemporary Lake Kushu (Fig. 1D). These works present coarse-resolution records of dia- toms and sulfur content providing rough information about the evolu- tion of the lake system. The BHAP focuses on high-resolution, chron- ologically well-constrained analyses of the RK12 core representing the Lake Kushu lacustrine sedimentary succession. Pilot studies (Müller et al., 2016; Schmidt et al., 2016) have tested and approved the high potential of RK12 to serve these aims and to allow reconstructing past variations in vegetation and climate conditions as well as the evolution of the lake system over the past ca. 16,600 years. Recently, BHAP members have presented a high-resolution terrestrial pollen record from the RK12 core spanning the last 6000 years, which was employed to reconstruct vegetation and climate changes and human–environment interactions on the island (Leipe et al., 2017; Leipe et al., 2018). Regarding the prehistory of Rebun Island, the record of regional https://doi.org/10.1016/j.palaeo.2018.11.010 Received 23 August 2018; Received in revised form 9 November 2018; Accepted 10 November 2018 ⁎ Corresponding authors. E-mail addresses: mareike.schmidt22@gmail.com (M. Schmidt), ptarasov@zedat.fu-berlin.de (P.E. Tarasov). Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 613–626 Available online 12 November 2018 0031-0182/ © 2018 Elsevier B.V. All rights reserved. T