JOURNAL OF QUATERNARY SCIENCE (2021) 36(4) 570–585 ISSN 0267-8179. DOI: 10.1002/jqs.3317 The Oyambre coastal terrace: a detailed sedimentary record of the Last Interglacial Stage in northern Iberia (Cantabrian coast, Spain) ELISA SAINZ DE MURIETA,* PEDRO P. CUNHA, 2 ALEJANDRO CEARRETA, 1,3 ANDREW S. MURRAY 4 and JAN‐PIETER BUYLAERT 5 1 Basque Centre for Climate Change (BC3), Edificio Sede 1, Bº Sarriena s/n, Leioa, Basque Country, Spain 2 University of Coimbra, MARE ‐ Marine and Environmental Sciences Centre, Department of Earth Sciences, Univ. Coimbra ‐ Pólo II, Coimbra, Portugal 3 Departamento de Geología, Facultad de Ciência y Tecnología, Universidad del País Vasco UPV/EHU, Bilbao, Spain 4 Nordic Laboratory for Luminescence Dating, Department of Geoscience, Aarhus University, DTU Risø Campus, Roskilde, Denmark 5 Department of Physics, Technical University of Denmark, DTU Risø Campus, Roskilde, Denmark Received 31 March 2020; Revised 13 March 2021; Accepted 15 March 2021 ABSTRACT: A detailed study is presented of a 15.3‐m‐thick Pleistocene coastal terrace located on the Cantabrian coast (northern Spain). Stratigraphic, sedimentological, topographic and micropalaeontological information is combined with a chronology based on luminescence dating to characterize the deposits. The sedimentary succession records: (i) a basal transgressive system, consisting of a wave‐cut surface covered by a lower layer of beach gravels and upper beach pebbly sands; and (ii) a thicker upper highstand system (aggrading), comprising medium to very fine aeolian sands interbedded with thin palustrine muds. Luminescence dating involved a detailed sampling strategy (36 samples and two modern analogues) and the use of both quartz optically stimulated luminescence (OSL) and feldspar post‐infrared infrared stimulated luminescence single aliquot regeneration protocols; feldspar results were used to confirm the completeness of bleaching of the quartz OSL signal. The quartz OSL luminescence age–depth relationship shows significant dispersion, but nevertheless two rapid phases of deposition can be clearly identified: one at ~130 ka [Marine Oxygen Isotope Stage (MIS) 5] and one at ~100 ka (MIS 5c). The top of the succession is dated to ~70 ka. The MIS 5e marine maximum flooding surface is identified at an elevation of 6.85 m above mean seal level. This elevation provides evidence of a regional sea‐level highstand for this sector of the Cantabrian coast. © 2021 The Authors. Journal of Quaternary Science Published by John Wiley & Sons Ltd. KEYWORDS: coastal terrace; Last Interglacial Stage (LIG); MIS 5 regional sea‐level highstand; northern Iberia; OSL dating Introduction Among the multiple changes already triggered by global warming, sea‐level rise (SLR) represents a serious risk for coastal areas around the world; these concentrate a great part of global population and socioeconomic infrastructures (Revi et al., 2014). The Quaternary (the last 2.58 Ma) has been characterized by frequent and rapid changes in Earth's climate and one of the many consequences resulting from these is the variation in global sea levels through time. Many Earth system components, such as orbital parameters, radiative forcing, landmass topography or ocean circulation, were different in the past and thus direct analogies between past and future climate changes should be avoided (Oldfield, 2005; Yin and Berger, 2015). Nevertheless, past analogues do provide the insights required to improve our knowledge of natural climate variability and its driving mechanisms. Future climate change will result from the interaction between natural processes and human activities, and without a sound understanding of these natural processes, it will be very difficult to identify and quantify the anthropogenic contribution. Thus, a better understanding of these interactions will contribute to improve- ments in the process‐based models currently used to estimate future projections (Edwards et al., 2001; Gilford et al., 2020). It is therefore not only useful, but necessary, to look at the past to fully comprehend how the undisturbed Earth system func- tioned before human forcing became significant (Loutre and Berger, 2003; Oldfield, 2005). Particular attention has been paid to Marine Oxygen Isotope Stage (MIS) 11, when sea‐level highstand peaked at 410 ka (Loutre and Berger, 2003; Tzedakis, 2010; Candy et al., 2014) and MIS 5, the Last Interglacial, ~125 ka (Kukla et al., 2002; Tzedakis, 2003). The Last Interglacial Stage (LIG), or MIS 5, is considered ‘the most recent geological interval during which conditions were similar to the present interglacial’ (Tzedakis, 2003). CO 2 concentration during the LIG was similar to pre‐ industrial levels but warming had a strong orbital forcing and because of this, the analogy with the late Holocene climate has been questioned (Loutre and Berger, 2003). However, and despite these qualifications, the warm climate of MIS 5 (together with that of MIS 9 and MIS 11) is similar to that resulting from ‘the anthropogenic warming in terms of climate feedbacks at the regional scale’ (Yin and Berger, 2015). Global mean temperatures during this stage were at least 2 °C higher than present (Rohling et al., 2008), Greenland and West Antarctic ice sheets were reduced in size (Goelzer et al., 2016), sea level was, most probably, more than 5 m above current mean level (Cuffey and Marshall, 2000; Hearty et al., 2007; Masson‐Delmotte et al., 2013; © 2021 The Authors. Journal of Quaternary Science Published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made. * Correspondence to: Elisa Sainz de Murieta, as above. E‐mail: elisa.sainzdemurieta@bc3research.org