The significance of palaeoecological indicators in reconstructing estuarine environments: A multi-proxy study of increased Middle Holocene tidal influence in the lower Scheldt river, N-Belgium Annelies Storme a, * , Jan Bastiaens b , Philippe Cromb  e c , Fr  ed  eric Cruz d , Stephen Louwye a , Jeroen Verhegge c , Koen Deforce b, c, e a Department of Geology, Ghent University, Krijgslaan 281-S8, 9000, Ghent, Belgium b Flanders Heritage Agency, Havenlaan 88, Bus 5, 1000, Brussels, Belgium c Department of Archaeology, Ghent University, Sint-Pietersnieuwstraat 35, 9000, Ghent, Belgium d GATE Archaeology, Hurstweg 8, 9000, Ghent, Belgium e Royal Belgian Institute of Natural Sciences, Vautierstraat 29, 1000, Brussels, Belgium article info Article history: Received 10 July 2019 Received in revised form 26 November 2019 Accepted 27 November 2019 Keywords: Middle holocene Northwest europe Pollen Diatoms Botanical macroremains Estuary Scheldt Tidal action Salinity Prehistory abstract Interpretation of fossil assemblages in mixed energy environments, such as estuaries, is complex due to the accumulation of material from different sources. In such environments, different proxies may result in contrasting interpretations, as is illustrated by the case of the Scheldt estuary in northern Belgium: during a phase of increased landward tidal ingression between 7000 and 5000 cal BP, mud was deposited, including microfossils that indicate increased salinity, while macrofossil records from the same deposits indicate tidal freshwater environments. By combining multiple proxies, sedimentological analysis and multivariate statistics, it is concluded that considerable landward sediment transport by tidal pumping, possibly enhanced by storms, explains how marine and brackish microfossils are massively present in freshwater tidal deposits. We propose an approach that combines the easily transported microfossils with the more local macrofossils to obtain a coherent reconstruction of the local estuarine environment, and to better understand the sedimentological processes in the wider region. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction Estuaries are complex environments where marine and fluvial processes interact with each other and influence almost every aspect of the local plant and animal communities and thus the human habitat (Dalrymple and Choi, 2007; de Haas et al., 2018; Meire et al., 2005; Pritchard, 1967). Reconstructing these environ- ments from the past through the study of palaeoecological proxies from estuarine deposits in cores or (archaeological) excavations is a complex task because many factors, such as tidal energy, dominant flow direction, sediment transport and salinity, influence the dis- tribution of biological remains in the sedimentary record (Dupont et al., 1994; Hassan et al., 2008; Medeanic et al., 2016; Odum, 1988; Sawai et al., 2016). Diatoms are used worldwide to reconstruct past environments in the fluvial-marine transitional zone, since these aquatic organ- isms have a high indicator value for salinity and tidal regime (e.g. Byrne et al., 2001; Zong et al., 2006; Hill et al., 2007; Hassan, 2010). In addition, molluscs are also good indicators of the aquatic envi- ronment (e.g. Umitsu et al., 2001; Espinosa et al., 2003); pollen and non-pollen palynomorphs (e.g. de Vernal and Giroux, 1991; Byrne et al., 2001; Kraus et al., 2003) and botanical macroremains (e.g. Behre, 1986; Sawai et al., 2002) represent the regional and local vegetation and animal remains reflect their habitat. Beside these commonly studied proxies, a number of other types that are not used in this paper, may also be used as palaeoecological indicators (e.g. ostracods, foraminifera, phytoliths). The challenge is to select the most advantageous (combination of) proxies to distinguish * Corresponding author. E-mail address: annelies.storme@ugent.be (A. Storme). Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev https://doi.org/10.1016/j.quascirev.2019.106113 0277-3791/© 2019 Elsevier Ltd. All rights reserved. Quaternary Science Reviews 230 (2020) 106113