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The calcareous tufa sequence and associated Palaeolithic site of Caours were discovered in 2002 during a test‐pit campaign aimed at identifying last interglacial (MIS 5e) archives in the fluvial terrace system of the Somme basin, northern France. The presence of an outstanding stratigraphical succession with four in situ Palaeolithic layers within the tufa sequence has motivated archaeological excavations of the site since 2005. The first malacological studies and U‐series ages quickly showed that the sequence was mainly deposited during the Eemian interglacial (MIS 5e). After 20 years of investigations, we propose here a summary of this multidisciplinary research project including stratigraphy, sedimentology, geochronology, geochemistry, malacology, mammals, palaeovegetation and archaeology. By combining 25 dates obtained by U‐series, ESR/U‐series, TL and OSL methods, the Caours calcareous tufa sequence is securely dated to the Eemian (123.1±2.8 ka). Based on the summary of the whole information, we propose a robust and detailed reconstruction of the modification of the valley environments between the Late Saalian and the Early Weichselian. At the scale of northwestern Europe, Caours provides a reference terrestrial molluscs record for the Eemian interglacial, including the climatic optimum, that is also described in the same layers by δ18O and δ13C analyses on calcite and by mammal remains. Moreover, the 300‐m‐long transect crossing the fluvial terrace covered by the tufa sequence and the bottom valley formation, combined with the chronology established from U‐series and OSL ages, shows that the incision of the present‐day valley, leading to the setting of the Very Low Terrace, was achieved during the first stages of the Early Weichselian (MIS 5d–5c). From an archaeological point of view, the configuration of the Caours site is unique at the scale of western Europe and demonstrates the adaptation of Neandertals to a forested environment and to fully temperate conditions during the Eemian. [ABSTRACT FROM AUTHOR]

Calcareous tufas are continental carbonates from open-air conditions, specific to wet and warm periods. They contain abundant remains of fauna and flora fossilised in situ and may accumulate regularly over thousands of years offering high stratigraphic resolution for palaeoenvironmental reconstructions. As they are mainly comprised of calcite, tufas allow direct and precise dating as well as geochemical reconstructions of past climates. Additionally, recent investigations have highlighted their strong potential for archaeology as several studied sequences provided high quality record of in situ prehistoric levels. Tufas are thus a unique archive in continental areas for development of synergic multidisciplinary investigations of past human societies and associated environmental and climate evolution. We emphasise that calcareous tufa are key-deposits to investigate human–environment–climate interactions during interglacial periods, from Lower Palaeolithic to Antiquity, in Europe. [ABSTRACT FROM AUTHOR]

In north-western Europe, continental records of Pleistocene interglacials are well preserved in fluvial sequences and particularly within calcareous tufas that formed at the top of the series. They are the sole deposits recording the full optima. Tufas contain rich malacological communities that allow the detailed palaeoenvironmental history of past interglacials to be reconstructed. Several tufas have been investigated in the study area, which have led to the recognition of the « Lyrodiscus fauna » as a characteristic biostratigraphical signature of tufa sequences of MIS 11 age in north-western Europe. Among these, the site at La Celle in the Seine valley (France) is the only one where tufa has accumulated a substantial thickness (almost 9 m) in which the complete development of the Lyrodiscus fauna is represented, yielding a detailed record of the forest expansion during the MIS 11 interglacial. The La Celle succession therefore provides a regional framework into which other sequences can be set, shedding lights on various aspects of palaeoenvironmental dynamics, biostratigraphy, palaeogeography and palaeobiodiversity. Combined malacological and isotopic records from La Celle demonstrate a close correlation between increasing temperatures and the development of forest land snail communities. The palaeoecological framework of forest extension inferred from the malacological succession of La Celle allows the shorter successions from northern France and south-eastern England to be located within the maximum development of the humid forest biotope during MIS 11c. The order of occurrence of forest snails indicates that Atlantic and Central European refugia are the original sources of recolonizations for north-western European sites. Strict Mediterranean species reach the area only at the MIS 11c climatic optimum. Many species present during MIS 11c no longer live in this part of Europe, indicating a northward shift in the location of the modern alpine biodiversity hotspot. • The Lyrodiscus mollusc fauna is a biochronological reference for MIS 11 in NW Europe • La Celle is the sole deposit yielding a detailed record of MIS 11 forest expansion • Atlantic and Central refuges are the main sources of mollusc recolonization in NW Eur • Strict Mediterranean species reach NW Europe only at the climatic optimum • The malacological diversity hotspot during MIS 11 extends further north in NW Europe [ABSTRACT FROM AUTHOR]

In 1993, Goudie and co-authors named the postulate that there would be a marked decline in the deposition of calcareous tufa in Europe since ca. 2500 BP 'the late-Holocene tufa decline'. However, the growing development of investigation on calcareous tufas and considerable improvement in dating methods, especially radiocarbon dating, has provided reliable evidence of deposits developing until our present days. I thus discuss the reality of the decline, reviewing 62 tufa sites in Europe and their time distribution based both on radiocarbon dates and biochronological data and distinguishing different cases depending on tufa size and types. I demonstrate that the late-Holocene tufa decline is actually a general view of a rather complex tendency: after a maximum during the Atlantic period, fluvial tufas are systematically affected by a decline from ca. 5 ka cal. BP but no general trend is shown in the development of proximal (spring-fed) or lacustrine tufas. This observation is likely to result from the increasing impact of human activity (mainly deforestation) on landscapes, and more specifically on fluvial environments, from the Bronze Age. • Date frequency is not appropriate to discuss tufa distribution during the Holocene. • The late-Holocene tufa decline in Europe systematically affects fluvial tufas only. • No systematic decline is observed in proximal (spring) and lacustrine tufas. • Fluvial tufa deposits are likely to be more exposed to anthropogenic changes. [ABSTRACT FROM AUTHOR]