# Sedimentary processes and palaeoenvironments from La Combette sequence (southeastern France): climatic insights on the Last Interglacial/Glacial transition

Carlo Mologni, Louise Purdue, Benjamin Audiard, Michel Dubar, Sebastian Kreutzer, Pierre-Jean Texier

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Carlo Mologni, Louise Purdue, Benjamin Audiard, Michel Dubar, Sebastian Kreutzer, et al.. Sedimentary processes and palaeoenvironments from La Combette sequence (southeastern France): climatic insights on the Last Interglacial/Glacial transition. Palaeogeography, Palaeoclimatology, Palaeoecology, 2021, 576, pp.110503. 10.1016/j.palaeo.2021.110503. hal-03585835

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# Sedimentary processes and palaeoenvironments from La Combette sequence (southeastern France)

Mologni, Carlo; Purdue, Louise; Audiard, Benjamin; Dubar, Michel; Kreutzer, Sebastian; Texier, Pierre-jean

**Published in:**

Palaeogeography, Palaeoclimatology, Palaeoecology

**DOI:**

10.1016/j.palaeo.2021.110503

**Publication date:**

2021

**Citation for published version (APA):**

Mologni, C., Purdue, L., Audiard, B., Dubar, M., Kreutzer, S., & Texier, P. (2021). Sedimentary processes and palaeoenvironments from La Combette sequence (southeastern France): Climatic insights on the Last Interglacial/Glacial transition. *Palaeogeography, Palaeoclimatology, Palaeoecology*, 576, Article 110503.

https://doi.org/10.1016/j.palaeo.2021.110503

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1 Sedimentary processes and palaeoenvironments from La

2 Combette sequence (southeastern France): climatic insights on

3 the Last Interglacial/Glacial transition

4 Carlo Mologni<sup>a, b *</sup>, Louise Purdue<sup>b</sup>, Benjamin Audiard<sup>b</sup>, Michel Dubar<sup>b</sup>, Sebastian Kreutzer<sup>c,d</sup>, Pierre-

5 Jean Texier<sup>e</sup>

6

7 <sup>a</sup>Université Côte d'Azur, CNRS, Observatoire de la Côte d'Azur, IRD, Géoazur, 250 rue Albert Einstein, 06905 Sophia Antipolis,

8 France

9 <sup>b</sup>Université Côte d'Azur, CNRS, CEPAM-UMR7264, 24 avenue des Diables Bleus 06357, Nice, France.

10 <sup>c</sup>Geography & Earth Sciences, Aberystwyth University, SY23 3DB, Wales, United Kingdom

11 <sup>d</sup>Université Bordeaux Montaigne, CNRS, IRAMAT-CRP2A-UMR5060, Maison de l'Archéologie, Esplanade des Antilles, 33607

12 Pessac Cedex, France

13 <sup>e</sup>Aix Marseille Univ, CNRS, Minist Culture, LAMPEA, UMR 72-69, 5 rue du château de l'horloge, 13094 Aix-en-Provence, France

14

15 *corresponding author: Carlo Mologni: mologni@geoazur.unice.fr

16 Louise Purdue (louise.purdue@cepam.cnrs.fr)

17 Benjamin Audiard (bejamin.audiard@cepam.cnrs.fr)

18 Michel Dubar (michel.dubar@cepam.cnrs.fr)

19 Sebastian Kreutzer (sebastian.kreutzer@aber.ac.uk)

20 Pierre-Jean Texier (pj.texier@gmail.com)

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22

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24

25
26 **Abstract**

During the Last Interglacial-Early Glacial transition (MIS5-MIS4; ~73 ka), substantial hydroclimatic changes affected morphogenetic processes, landform dynamics, and ecosystem variability over the Mediterranean sub-alpine valleys. This transition is mainly preserved in the northern Mediterranean region in continuous marine, lacustrine, and peat bog archives. To understand better local-to-regional hydro-sedimentary processes, their climatic significance, and their direct impact on prehistoric settlements, this manuscript reinvestigates a known continental sedimentary record with revised methods. The Middle Palaeolithic site of La Combette in the western Provence region (southeastern France) presents a thick sedimentary sequence key for studying environmental changes from the MIS5 to the MIS3. A review of previous studies with the integration of new micromorphological, sedimentological, physicochemical, malacological, and luminescence ages allows us to characterize the sedimentary processes and environmental patterns during this major climatic transition. Alternating warm and cold conditions and shifting vegetation patterns reflect the strong environmental instability of the end of the Last Interglacial Period. The emergence of a steppe-like ecology dominated by cryo-turbated loess deposition marks the beginning of the Early Würmian Glacial period (MIS4-MIS3; ~73 ka to ~50 ka), contemporaneous with the last Neanderthal occupation at La Combette rock shelter. Comparisons with regional palaeoclimatic data allow us to detail local climatic settings and provide evidence of divergences with larger-scale quantitative reconstructions during a period of significant environmental and socio-cultural shifts.

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44 **Keywords:** MIS 5-3; Multiproxy; Neanderthal; Loess; Micromorphology; Chronology

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46 **1 - Introduction**

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Confronting global climate models with regional environmental trends is essential to understand the evolution of palaeolandscapes and their impact on the development of ecosystems and prehistoric population dynamics. Interglacial-glacial transitions represent sensitive periods for the comprehension of landforms’ reactivity to global hydroclimatic variations (Klotz et al., 2004) in relation to prehistoric peopling. In particular, the Last

Accepted manuscript version prior to proof-reading.

For the published version see: https://doi.org/10.1016/j.palaeo.2021.110503
53 Interglacial-Glacial transition (LI-G; MIS5-MIS4-MIS3, ~90 – ~50 ka) shows several sub-stage
54 oscillations, sometimes abrupt (Reille et al., 1992; Salonen et al., 2018), mainly towards the
55 onset of glacial Würmian conditions.

56 In southeastern France, only a few continuous sedimentary records have recorded the
57 LI-G climatic transition. One submarine core covering this cycle was extracted from the deep
58 Rhône delta (Gulf of Lion, MD99-2348 core; Sierro et al., 2009; Fig. 1). It reveals temperate
59 conditions and high fluvial activity during the interglacial MIS 5, followed by reduced
60 hydrological activity and a shift towards cooler and drier conditions during the MIS5 – MIS4
61 transition. Further north, in the septentrional Rhône basin, the palynological study of the peats
62 sequences of Les Echets (Beaulieu and Reille, 1984; de Beaulieu and Reille, 1989) and La Grande
63 Pile (Fauquette et al., 1999; Helmens, 2014; Seret et al., 1990; Woillard and Mook, 1982; Fig.
64 1) indicate a substantial reduction of rainfall and temperatures (Fauquette et al., 1999) with
65 the spread of steppe taxa. However, the beginning MIS4 seems to be interspersed by slight
66 warmer oscillations, attesting a period of progressive environmental stabilisation thought the
67 glacial conditions, definitely installed around ~60 ka (Fauquette et al., 1999; Helmens, 2014). A
68 recent study on a loess-paleosol sequence in the Lower Rhône valley provides the first robust
69 loess chronosequence from the Early Würmian glaciation in the south of France confirming this
70 transition (Bosq et al., 2020b). However, most sedimentary records in southeastern France
71 covering this period and linked to Neanderthal occupations (archaeological stratigraphy) are
72 non-continuous and incomplete, adding a considerable uncertainty to the environmental
73 interpretations (Fig. 1). For instance, this is the case at Bau de l'Aubesier (MIS5 or 6; Lebel and
74 Trinkaus, 2002), the Grand abri aux Puces (MIS5e; Slimak et al., 2010), the Baume Bonne (from
75 MIS 10, lack of MIS 5-4; Gagnepain and Gaillard, 2003), Les Auzières 2 (MIS4; Marchal et al.,
2009), and the Payre (MIS6-MIS5; Moncel et al., 2008). Apart from a few well-dated sites such as Moula-Guercy (Saos et al., 2014; Willmes et al., 2016), the Baume Flandin, the Pêcheurs, and the Maras rock shelters (Moncel et al., 2010), most of the excavated sequences lack absolute dating, e.g., Baume des Peyrards (de Lumley, 1969, 1957), Adaouste Cave (Conrad and Onoratini, 1997; Defleur et al., 1994), La Verrerie (Crégut-Bonnoure, 2002). Understanding the regional-to-local environmental patterns of prehistoric occupations during prominent climatic disruptions is fundamental for interpreting archaeological records. Moreover, most of these archaeological sites need to high-resolution studies, which are the key to decipher this complex climatic transition. In the Mediterranean region, cave and rock shelter sediments have the potential to record abrupt climatic changes, in particular, if investigated by a microstratigraphic perspective (Courty and Vallverdu, 2001; Macklin and Woodward, 2009; Woodward et al., 2001).

With the aim to provide new data and fuel the debate on the palaeoenvironmental background of the LI-G Neanderthal occupations, we reinvestigated the continental sequence of the La Combette rock shelter through a new chronology (Kreutzer et al., 2021). Based on a review of previous palynological (López-Sáez et al., 1998) and charcoal analyses (Audiard et al., 2019; Théry-Parisot and Texier, 2006) and the data improvement with new micromorphological, sedimentological, physicochemical, and malacological analyses, we propose a detailed palaeoenvironmental evolution of the La Combette sequence in connection with LI-G broader hydro-climatic shifts. Our results combine previous regional records in order to identify and discuss the local and/or regional impact of climatic change on the local landscape dynamics, adding to our comprehension of the complex environmental nuances of the Last Interglacial – Glacial transition in the Mediterranean.
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## 2 – Regional settings and site description

At an elevation of 327 m a.s.l., the rock shelter is located along the La Combette stream, in the Aigue Brun valley, a tributary of the Durance river, part of the Rhône river hydrological system (Figs. 1, 2a). The stream originates locally from the Luberon Massif, a few kilometers from the shelter, which borders the northern sub-alpine domain of the Vaucluse Mountains and the southern Provençal-Littoral domain. The river course crosses Urgonian (Lower Cretaceous), Oligocene, and Miocene molasses calcareous rocks, which compose the rock shelter. Due to the N-S mistral wind regime (16 m/s for >100 d/y; Jacq et al., 2005), the area is constituted of numerous ancient aeolian landforms like sand wedges, ventifacts, loess deposits, and freeze/thaw structures (Bertran et al., 2016; Bosq et al., 2020b, 2020a, 2018; Fig. 1). The lithostratigraphic sequence of La Combette belongs to these periglacial morphosedimentary features (Fig. 1, 2; Buoncristiani and Campy, 2011; Cossart et al., 2011, 2008; Tiercelin, 1977).

Multidisciplinary studies in La Combette rock shelter were conducted between the 1990 to 2002. Combined techno-functional (lithic technology and traceology), archaeo-petrographic, anthracological, palynological, archaeozoological, and thermally stimulated luminescence (TL) analyses (Lemorini, 2000; López-Sáez et al., 1998; Texier et al., 2003; Théry-Parisot and Texier, 2006; Wilson et al., 2018) provided unique knowledge on Neanderthal subsistence strategies in southeastern France (Daujeard et al., 2012; Théry-Parisot and Texier, 2006; Wilson et al., 2018). However, a detailed sedimentological and geochronological study of the sequence, as well as their palaeoclimatic relevance, had never been attempted until today.

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123 3 - Material and methods

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125 3.1 – Field methods and sampling strategy

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During the excavation in the 1990s, two prominent sedimentary ensembles (Upper and Lower) with eight archaeological levels were differentiated (A to H; Texier et al., 2003). In 2019, a field campaign allowed us to examine more precisely this sedimentary sequence and define 19 new sedimentary units (SU; Fig. 3) based on texture, structure, color, sorting, boundaries, and inclusions (ecological, sedimentary, or anthropic).

The new stratigraphic layers were sampled for magnetic susceptibility, sedimentological, pedological and palaeoecological studies. The magnetic susceptibility (SI) was measured in the field every 5 cm with a Bartington MS2 Instrument (10-5 SI), except on gravelly deposits to avoid magnetic anomalies. Thin section samples were carved in the lower and upper ensemble from the eastern section of La Combette (Fig. 3). Bulk sediments were sampled for sedimentary analyses (grain size, heavy minerals, CaCO₃ content) next to the micromorphological samples (Fig. 3). A total of 17 micromorphological blocks and 48 bulk sediments were sampled.

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From the northern section of La Combette, 22 bulk sediment samples were collected (10 l sediment each sample) along with the Lower and Upper ensembles for palaeological study. Malacofauna samples were sieved with 0.8 mm sieves, manually sorted, and identified under a binocular microscope.

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To refine the geochronological framework and test whether the Lower Ensemble might belong to the MIS 6/7 (a hypothesis put forward by Walther, 1995), the sedimentary section
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was re-investigated by Kreutzer et al., 2021. Six new samples were taken from the main
archaeological levels for luminescence dating (Table 1).

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## 3.2 – Laboratory methods

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### 3.2.1 – Micromorphology

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Soil thin sections were prepared following the standard procedure described in
(Guillore, 1980). Seventeen thin sections were studied under a polarizing microscope Zeiss
Axioskop 40 Pol/ 40 A Pol at a magnification between 25x and 1000x using plane-polarized
(PPL), crossed-polarized (XPL), and fluorescence light (UV). Thin sections are described
following the guidelines proposed by Bullock (1985) and Stoops (2003).

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### 3.2.2 – Physicochemical analysis

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Grain size analysis was performed on a Beckman Coulter LS200 laser diffraction particle
size analyzer. Samples were deflocculated with sodium hexametaphosphate solution and
decarbonized with HCl (1 mol; Konert and Vandenberghe, 1997). Given the limited amount of
organic material (cf. micromorphological observations; section 4.2), organic components were
not destroyed. Furthermore, to ensure that authigenic carbonates did not bias the particle size
signal, grain size measurements were performed on both carbonated and decarbonated
samples.

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The CaCO₃ concentration in sediments was determined using a Bernard calcimeter
(Cailleux and Tricart, 1964). The samples were sieved at 2 mm, crushed, weighed, and dissolved

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166 in an HCl ½ solution. The CO₂ volume was measured, and the calcimeter was calibrated by
167 measuring the CO₂ volume of pure calcium carbonate.

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169 **3.2.3 – Heavy-mineral analysis**

170 Sample preparation for heavy-mineral determination followed the procedure described
171 in Cailleux and Tricart (1964) and Parfenoff et al. (1970). Because of the silt and fine sand
172 texture of the deposits, we analyzed the 200-40 µm fraction. Samples (100 g) were
173 decarbonized in HCl at 20°C and 80°C, while heavy minerals were separated by immersion and
174 decantation in a tribromomethane solution (CHBr₃, 2.89 g/cm³) and fixed on non-polished thin
175 sections with a natural isotropic resin. Mineral identification was performed under a polarizing
176 microscope Zeiss Axioskop 40 Pol/ 40 A Pol on samples of 150 grains per section. The local
177 mineral assemblage was identified based on the heavy mineral extraction of molassic parent
178 rock material from the rock shelter vault and the bedrock of Aigue Brun canyon.

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180 **3.2.4 – Luminescence dating details**

181 For luminescence dating, Kreutzer et al. (2021) extracted the fine grain (4–11 µm)
182 quartz and polymineral fraction following routine luminescence sample preparation methods
183 (Preusser et al., 2008). The quartz fraction was measured with optically stimulated
184 luminescence (OSL; Huntley et al., 1985) applying the single-aliquot regenerative- (SAR, Murray
185 and Wintle, 2000) dose protocol. The polymineral fraction was measured with infrared
186 stimulated luminescence (IRSL; Hütt et al., 1986), applying the post-IR IRSL protocol at 225 °C
187 (Buylaert et al., 2009; Thomsen et al., 2008). Measurements were carried out on a Freiberg
188 Instrument *lexsyg SMART* OSL/TL reader (Richter et al., 2015). Dose rates were measured in
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situ with passive carbon-doped dosimeters (for the procedure, see Kreutzer et al., 2018) in conjunction with high-resolution gamma-ray spectrometry. The ages results, corresponding to the archaeological layers, are presented in Table 1.

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## 4 - Results

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### 4.1 - Stratigraphy and geochronology

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Based on the redefinition of the stratigraphy in 2019, we kept the initial lower and upper ensemble, but the former was divided into three sub-ensembles identified by the roman numbers I, II, III (Fig. 2b, 3; see Sup. Mat. Table A.1 for detailed SU pedo-sedimentary description).

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From the bottom to the top, the Sub-ensemble-I is composed of three colluvial stratigraphic units (SU19-18-17) characterized by a) poor textural variability, mainly weakly-sorted sandy silts with gravel inclusions, b) absence of layering, c) high density of archaeological remains (layer F/G; Texier et al., 2003). Traces of vault collapse prior to the shelter sedimentary fill were observed. One luminescence date was obtained in stratum 17 and provided 71.9 ± 5.5 ka (BDX16816; Fig. 3b, Table 1) corresponding to the top of the archaeological layer F/G described in Texier et al., (2003).

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Sub-ensemble-II.a (SU16, 15, 14, 13, 12, 11, 10) is characterized by fine alternating sands and silts typical of a layered rhythmic deposition. Following an erosional contact, Sub-ensemble-II.b (9, 8) is a coarser and massive deposit composed of sub-angular clasts in a sandy-silty matrix. Numerous Mousterian artifacts and combustion structures were discovered in SU8

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corresponding to archaeological layer E (Texier et al. 2003), which was dated from 80.1 ± 6.4 ka (BDX16815; Fig. 3b, Table 1)

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Sub-ensemble-III (SU7-6; Fig. 3b) comprises gravels and molassic blocs (10 cm to 50 cm) in a coarse-sandy matrix, mainly located in the southern part of the shelter. These layers appear as a clast-supported deposit then subsequently filled in by silty sediments from the Upper Ensemble. A luminescence date obtained from the fine silty fraction provided an age of 64.5 ± 9.2 ka (SU7; BDX16814; Fig. 3b, Table 1), which is discussed in Section 5.2.1.

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Deposits in the Upper Ensemble are composed of 2.5-meter-thick loess deposits (Fig. 3a; SU 5-4-3-2) characterized by a) homogenous sedimentary textures with no coarse material inclusions, b) accumulation of secondary carbonates, c) low density of archaeological material, mainly localized in SU5 and 4 (archaeological layer D in Texier et al. 2003). The Upper ensemble was dated from 66.1 ± 5.4 ka (SU4; BDX16813), 66.5 ± 6.8 ka (SU2, 210cm depth; BDX16812) and 57.4 ± 5.4 ka (SU2, 130 cm depth; BDX16811; Fig. 3a, Table 1). SU1 corresponds to the current erosional surface and Ah horizon covering the outer part of the rock shelter sequence.

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## 4.2 – Micromorphology

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In order to provide a clearer presentation of sedimentary modes and dynamics of deposition versus pedoclimatic conditions corresponding to syn- or post-depositional climate-related processes, we classified our micromorphological observations in Micromorphological Sedimentary Facies (MSF) and Micromorphological Pedoclimatic Facies (MPF). The facies are presented below, and respective micromorphological descriptions are synthesized in Sup. Mat. Tables A.2, A.3, A.4, A.5.
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## 4.2.1 – Micromorphological Sedimentary Facies (MSF)

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**MSF-1 Fluvial deposits:** Two types of fluvial deposits have been identified: low energy fluvial deposits (MSF-1.a; Fig. 4a) and high energy fluvial deposits (MSF-1.b; Fig. 4a). The first type is characterized by a well-sorted coarse fraction organized in positively graded beds composed of fine sand (80%; 63-100 µm, grain size average 80 µm). The sands comprise sub-angular quartz grains following a coarse monic c/f related distribution pattern and 10-20% of the molassic local parent material. The packing void porosity and the lack of coatings on clastic grains also characterize these facies. The MSF-1.b sub-facies is moderately sorted with rare bedding. The coarse fraction is represented by medium and coarse sand (mean grain size 400 µm; 80%) principally composed of molassic local parent material (70-80%) and quartz grains (20-30%). The c/f related distribution pattern is coarse monic, around a simple packing voids porosity with almost no fine fraction. These coarse-fine laminae typical of Late Glacial floodwater inundation events (recognized in other Mediterranean canyons; Woodward et al., 2001) were produced by La Combette stream floods during periods of enhanced precipitations.

**MSF-2 Runoff and colluvium of loess and fine material:** Three types of runoff and colluvium deposits have been defined: silty-clay runoff deposit (MSF-2.a; Fig. 7a.2), laminated loess colluvium (MSF-2.b; Fig. 4b; Fig. 7a.1), and non-laminated loess colluvium (MSF-2.c; Fig. 4c; Fig. 7b.1). MSF-2.a refers to massive beds of very well sorted clay and fine silts (3-4 mm thick). The c/f related distribution pattern is fine monic to porphyric. MSF-2.b is very well sorted, organized in sub horizontal, thin laminations (1-2 mm) with fine silty-clay material on the top. This second
facies differs from the first one based on a) the enrichment in coarser particles of mica, feldspar, plagioclase, and glauconite; b) sub-rounded coarse material (c/f ratio 70/30); and c) rounded aggregates of fine material. MSF-2.c presents similar characteristics without laminations and is enriched in local molassic rock fragments, often recrystallized and pedorelicts or fragmented clay crusts.

MSF2.b and MSF2.c are characteristic of deposits subject to aeolian transport (Kemp, 1999; Pécsi, 1990; Pye, 1995) combined with syn- and post-depositional transport processes: runoff or colluvial. For these reasons, they are defined as *loess-like sediments* (Cremaschi, 1990). Laminated loess deposits may be the product of short rainfall events that have reworked the original aeolian deposit (Mücher et al., 2010; Mücher and Vreeken, 1981).

**MSF-3 Colluvium and Gravity-Induced deposits:** This facies gathers remobilized autochthonous parent material due to gravity and mass wasting dynamics. Two sub-facies are defined: coarse molassic slope deposits (MSF-3.a; Fig. 4d) and silty-sandy rock shelter filling (MSF-3.b; Fig. 4e). MSF-3.a is a non-sorted and non-laminated deposit principally composed of medium and coarse sand of local molassic origin (70-80%). The c/f related distribution pattern is coarse monic to chitonic with coarser grains capped or coated by silty clay. The microstructure is pellicular. MSF-3.b is poorly-sorted and non-laminated, composed of angular and sub-angular quartz grains (50-60%) that represent the finest coarse fraction (fine sand and silts), and rounded local molassic parent material (30-40%) that makes up the medium and coarse sand fraction. The fine fraction is well represented (c/f ratio 40/60), the c/f related distribution pattern is porphyric to enaulic, and porosity is organized under compound and complex packing
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voids. Planar non-accommodated voids often appear in a generally poorly developed granular microstructure.

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## 4.2.2 – Micromorphological Pedological and pedoclimatic Facies (MPF)

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**MPF-1 Bioturbation facies:** These facies was defined based on the degree of bioturbation observed in the thin sections. MPF-1.a represents the total bioturbation of the fabric, characterized by a heavy reorganization of the initial microstructure and the development of a spongy microstructure associated with coated channels (fine soil material on channel walls), chambers, earthworm casts, and micritic hypocoatings (Fig. 7). The latter corresponds to carbonate crystallization around the voids due to evapotranspiration processes (Kemp, 1999; Wieder and Yaalon, 1974). Partial bioturbation is defined by the MPF-1.b facies, recognizable by the initial porosity and microstructure, occasionally reworked by chambers and channels.

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**MPF-2 Freeze-Thaw features:** These pedoclimatic facies includes all features related to ice segregation processes, defined based on their magnitude. Three levels of ice segregation features have been identified: simple ice segregation (MPF-2.a; Fig. 5a, 5b), repeated freeze-thaw cycles (MPF-2.b; Fig. 5c, 5d), and solifluction (MPF-2.c; Fig. 6a-d). These facies are used as indicators of water supply and climatic conditions during cold periods (Van Vliet-Lanoë, 2010, 1985).

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Simple ice segregation (MPF-2.a) is recognizable by a planar or lenticular microstructure (Fig. 5a, 5b). Planar voids are non-accommodated to partially accommodated and are often associated with vertical/sub-vertical cracks or star-shaped soil structures. These structures

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form once the ice melts and are typical of a few freeze-thaw cycles and low water supply periods (Van Vliet-Lanoë et al., 2004). They define an ‘isoband fabric’ (Dumanski and St. Arnaud, 1966).

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The ‘bent fabric’ is the principal signature of MPF-2.b, which forms during the plastic transformation and migration of some fabric components of the original MPF-2.a patterns. During repeated freeze-thaw cycles, the fine fraction accumulates on top of irregular lenticular peds, while the coarse fraction is progressively englobed (FitzPatrick, 1976; Rowell and Dillon, 1972; Van Vliet-Lanoë, 1976; Fig. 5b, 5c). Settling with displacement structures (Van Vliet-Lanoë, 2010; Fig. 6a), turned silty-clay cappings (20–400 µm), ice blades, and granular microstructure are other markers typical of this facies. MPF-2.b is probably the result of long freeze-thaw cycles during periods of moderate water supply.

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MPF-2.c shows a heavy reorganization of the fabric: the coarse fraction is displaced vertically, mechanically fractured (Fig. 5c), and often associated with injection features (“water escape porosity” Phillips et al., 2007). Between the coarser molassic rock fragments, the finer fabric presents a striated b-fabric caused by the reorganization of fine particles under cryogenic and mass movement pressure (Tarnocai and Smith, 1989; van der Meer, 1997; Fig. 5b). Ice blades are bigger than those in the facies MPF-2.b, obliquely oriented and filled by coarse material (Fig. 5a), while silty-clay cappings are rotated (Fig. 5c). The bent fabric forms a well-developed granular microstructure (Fig. 5c), while turned cappings on grains are dissymmetric with a thicker part below the grain. This pedoclimatic facies results from the growing action of ice during multiple freeze-thaw cycles on slopes.

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**MPF-3 Secondary Carbonate features:** Two levels of secondary carbonate development have been defined. In the facies MPF-3.a, all the fabric is affected by secondary carbonate precipitation (micritic hypocoatings on voids and micritic coatings on clasts), forming a micritic crystallitic b-fabric (Fig. 7b.2). These features suggest multiple phases of water percolation saturated by carbonates (Monger et al., 1991; Wieder and Yaalon, 1974). MPF-3.b is characterized by rare micritic impregnations in the groundmass and scarce micritic/sparitic coatings/hypo-coatings around voids reflecting occasional carbonate dissolution and re-precipitation processes.

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### 4.2.3 – Micromorphology of La Combette sequence

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The Micromorphological facies defined for each SU are synthesized in Fig. 8j. The Lower Ensemble is composed of runoff, slope-wash, and solifluction deposits. SU19 is comprised of runoff (MSF-2.a) and gravity-induced deposits (MSF-3.a), disturbed by cryogenic processes in their upper part (MPF-2.b/.c). SU18 is a gravity-induced slope deposit (MSF-3.a) affected by solifluction (MPF-2.c) and repeated freeze-thaw cycles. A silty-sandy fill (MSF-3.b) and similar pedoclimatic facies (MPF-2.b and MPF-2.c) are recognized throughout SU17.

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338

339

340

341

Sub-ensemble-IIa is characterized alternating low (MSF-1.a) and high (MSF-1.b) energy flow sedimentation with no trace of pedoclimatic syn- or post-depositional features. SU8, composed of coarse molassic slope deposits (MSF-3.a), shows a reduced fluvial accretion and temporary degradation conditions (MPF-2.b).

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345

A shift in sedimentation processes characterizes the upper ensemble. Following the thick torrential sedimentary event (SU7), SU5 is composed of non-laminated loess colluvium (MSF-

346
347

2.c) affected by simple ice segregation (MPF-2.a). While SU3 presents traces of laminations

348

(MSF-2.b; Fig. 7a., A.2, A.3), simple ice segregation patterns are still recorded (MPF-2.a) as well

349

as secondary carbonate impregnations (MPF-3.b). SU2, the upper layer of the sequence, is

350

composed of non-laminated loess colluvium (MSF-2.c) highly affected by bioturbation (MPF-

351

1.a) and secondary carbonate precipitation (MPF-3.a; Fig. 7b.1, b.2).

352

353

## 4.3 - Magnetic, Physico-chemical, and sedimentological analyses

354

355

### 4.3.1 - Magnetic Susceptibility

356

357

Through the Lower Ensemble, four magnetic peaks were detected with intensities

358

comprised between 27 and 41 SI (Fig. 3b). Peak 1 and peak 2 correspond to SU19 and SU18,

359

while peak 3 corresponds to the interface between SU18 and SU17. Peak 4 marks the boundary

360

between Sub-ensembles-I and -II. These first peaks are measured in areas with high-density

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archaeological material. High magnetic values could be associated with anthropic heating-

362

induced activity (Brewer, 1964). This hypothesis is confirmed in SU8, where the highest

363

magnetic peak 7 (58 SI) was recorded in a layer composed almost entirely of a diamagnetic

364

clastic fraction (molasses, limestone) and numerous anthropic combustion structures. Peaks 5-

365

6, identified in the laminated fluvial sterile units of Sub-ensemble-II, could correspond to

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magnetic minerals eroded from oxic soils in the watershed (pedorelicts; Brewer, 1964) (Fig. 4a).

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In the upper ensemble, the main archaeological layer (SU5) is marked by peak 8, while SU3

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shows a slightly higher magnetic signal probably caused by oxide reduction processes (Fig. 3a).

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## 4.3.2 - CaCO₃ concentration

Total CaCO₃ concentration shows a substantial difference between the calcareous clastic composition of the Lower Ensemble (60% < CaCO₃ < 70%) and the loessic (mainly quartz) composition of the Upper Ensemble (30% < CaCO₃ < 45%), where the total CaCO₃ content is mainly the product of secondary carbonates (micromorphological observation; Fig. 8m).

## 4.3.3 Particle size from laser diffraction

Grain size analysis indicates weakly sorted deposits in Sub-ensemble-I (Fig. 8l). Sub-ensemble-II is marked by an increasing coarse fraction (coarse sand ~8%, medium sand ~20%, fine sand ~70%; Fig. 8l) as well as positive grading. The cumulative curves of the decarbonated SU5-4-3-2 reveal very well sorted silty sands (80-100µm; clay ~10%, silt ~50%, fine sand ~40%), confirming the aeolian origin of this clastic fraction typical of this region (Bosq et al., 2018). Only SU3 shows a slight increase in fine silty and clay material.

## 4.4 - Heavy-Mineral analysis

### 4.4.1 - Mineral assemblages

Three mineral assemblages were defined. Based on the existing literature on the Rhône/Durance river basins (Arnaud-Fassetta, 1998; Dubar, 1983; Van Andel, 1955) and the Provence region (Alimen, 1965; Dubar, 1983), two groups of allochthonous heavy minerals
were differentiated while our reference samples allowed us to define a local heavy mineral assemblage. a) The Massif Central and Rhône group is characterized by the combination of augite, aegyrinic augite, hypersthene, andalusite, basaltic hornblende, and garnet minerals. b) The Alpine group comprises glaucophane and epidote in the Durance basin and the southern French Alps, while epidote and hornblende are affiliated with the Isère basin and the northern French Alps. In order to facilitate the interpretation, we have grouped and considered hornblende, glaucophane, actinote, tremolite, chlorite, and choroid as part of the Alpine group.
c) local molassic heavy minerals are composed of 60–65% garnet, 20–30% resistant minerals (zircon, tourmaline, staurolite), and less than 10% typical alpine or upper Durance valley minerals (hornblende, glaucophane, actinote, tremolite), while epidote/zoisite constitutes 10–15%. Dubar (1983) has shown that molassic rocks from the lower Durance valley are composed of 51% epidote, 40% garnet and resistant minerals, and less than 2% minerals of Alpine origin.
This has allowed us to isolate the Luberon local group from the Alpine and the Massif Central/Rhône groups. This is even suggested by the recent geochemical study of loess from the Provence and Rhône regions, which evidenced the enrichment in resistant minerals (quartz, zircon, and Ti oxides; Alpine origin) in Last Glacial Maximum (LGM) aeolian deposits compared to local mineralogical catchment assemblages mainly composed of Ca-rich minerals (Bosq et al., 2020a).

411

### 4.4.2 – Evolution of the heavy mineral input in La Combette

413

As the source of the torrential stream flowing below the rock shelter of La Combette is found in the Luberon Massif and its upstream section is disconnected from the Durance or
416

Rhône river basin (Fig. 1), we suggest that deposits composed of heavy minerals from the Alpine or Massif Central /Rhône groups have undergone at least one aeolian transport cycle. In contrast, the deposits composed principally of local heavy minerals originate from fluviatile or gravity-induced transport from the Aiguebrun watershed.

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At the La Combette sequence base, the proportion of local heavy minerals reaches 60-62% (Sub-ensemble-I), with the Alpine input values typically reaching 20-33% (epidote/zoisite ~26%, other alpine minerals ~7%; Fig. 8k). The percentage of the local mineral input increases in Sub-ensemble-II (70-73%), while the alpine one decreases to 7% (epidote/zoisite 4%, alpine minerals 3%). The gradual disappearance of alpine minerals and the increasing local fraction suggests the erosion of local sediments and their transport over short distances during the deposition of Sub-ensemble-II. These results are in accordance with the grain-size analysis and the total CaCO₃ concentration analysis.

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In the upper Ensemble (starting in SU5), there is a shift in the mineral assemblage with 63% of Alpine group minerals (epidote/zoisite 52%, alpine minerals 11%) and 32% of local minerals (15% garnet, 17% resistant minerals; Fig. 8k). In SU3, the proportion of Alpine group minerals reaches 70%, while the local group decreases to 23%. These results suggest increasing eolian input and decreasing local hydrosedimentary processes. The contribution of the Massif Central /Rhône mineralogical group remains stable around 1% throughout the sequence.

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## 4.5 – Malacofauna study

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The malacofauna taxonomic determination is presented in Table 2 and Fig. 7i. A total of 56 individuals were identified, representing 11 species. The low amount of malacological

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remains does not allow us to provide a solid palaeoecological interpretation. However, some
observations can be pointed out and compared to the other complementary proxies.

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At the base of the sequence (SU 18 and 17), the combination of *Cepaea sp.*, *Pomatias elegans*, and *Chilostoma squamatimum* suggests a forest or shrubby environment persists until the top of Sub-ensemble-I. In Sub-ensemble-II (SU16 to SU8), the appearance of *Eumphalia strigella* indicates a sub-alpine-like environment characterized by open and shrubby areas. *Eumphalia strigella* is common in the non-pleniglacial Würmian fauna of the Lower Rhône Valley (Bourdier, 1958). The predominance of *Chilostoma squamatimum*, which is characteristic of an open forest environment (Limondin, 1990), is remarkable. In the Languedoc and Provence regions, this species evolves in hairy oak groves (André, 1983), which are considered semi-forested environments. The Upper Ensemble (SU5 to SU2) shows the disappearance of species typical of the forest and the decrease in *Chilostoma squamatimum* (Fig. 8i). The introduction of *Pupilla Triplicata*, *Clausilia parvula*, *Trochoidea geyeri*, and *Abida secale* associations characterizes these upper layers. These species are the most common ones of the Pleniglacial environment in the Provence region, while the substantial absence of *Granaria variabilis* and the reduction of *Chilostoma squamatimum* could indicate a freezing climate with a predominant herbaceous vegetation cover (Magnin, 1991).

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445

446

447

448

449

450

451

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456

457

## 5 – Discussion

458

### 5.1 – Depositional processes and local palaeoenvironmental conditions

459

Based on our results and previous studies (Lopez-Saez et al. 1998; Texier et al. 2003; Théry-Parisot and Texier, 2006; Audiard et al., 2019), we can now better describe the

460
461

sedimentary formation processes, the local hydro-system dynamics in the canyon of La Combette and their link with local palaeoecological and palaeoenvironmental settings (Fig. 8).

462

463

464

### 5.1.1 – Surface runoff dynamics and temperate/wet conditions

465

The base of the sedimentary fill of La Combette (SU19) corresponds to laminated runoff deposits. The absence of climate-related pedofeatures indicates the lack of extreme environmental conditions. These deposits were not dated, but a geochronological correlation is proposed in Section 5.2 based on palaeoenvironmental and ecological interpretations.

466

467

468

469

Palynological data indicate vegetation dominated by *Pinus sylvestris* t., coupled with *Carpinus betulus* t., *Juglans* t., *Castanea*, *Quercus* s., and *Pinus* sp., which reflects a cool environment that is warming up (Fig. 8h; Lopez-Saez et al., 1998). Charcoal data confirm these environmental conditions, with the presence of humid and temperate taxa (*Acer* sp., *Cornus* sp., *Ulmus* minor; Fig. 8f; Théry-Parisot and Texier, 2006). This temperate vegetation cover in a wet environment could reflect soil development and palaeolandscape stability in the watershed of La Combette.

470

471

472

473

474

475

476

### 5.1.2 – Freeze-thaw syn-sedimentary processes and cold/wet conditions

477

Within Sub-Ensemble-II, the development of solifluction and freeze-thaw processes indicate shifting environmental conditions between SU19 and SU18, possibly linked to mass wasting dynamics with moderate water availability.

478

479

480

From SU 18, the substantial increase in *Artemisia*, *Centaurea nigra* t., and *Papaveraceae* and the general decrease in temperate species suggest a colder environment (Lopez-Saez et al. 1998; Fig. 8h), while malacological data indicate a shrubby vegetation cover (Fig. 8i). Charcoal remains, with a slight decrease in mesophilic species and the appearance of *Salix* sp. (Fig. 8f;

481

482

483
Théry-Parisot and Texier, 2006), point towards a fresh to cold environment. This is also recorded in decreasing δ¹³C signal of these charcoal (Fig. 8g; isotopic Phase-I; Audiard et al., 2018). The slight increase in *Pinus nigra/sylvestris* combined with ice-segregation patterns indicates the persistence of these environmental conditions, with several fluctuations in moisture until the end of Sub-ensemble-I (SU 17; Fig. 8f). Chronologically, the top of this Sub-ensemble (71.9 ± 5.5 ka; 1-sigma) is younger than Sub-ensemble-II (80.1 ± 6.4 ka; 1-sigma), showing an ages inversion. However, the large uncertainties associated with these luminescence dates do not allow us to draw further conclusions.

492

### 5.1.2 – Alluvial sedimentation and temperate/wet conditions

Sub-ensemble-II and -III record alluvial sedimentation with the occurrence of medium and high-intensity floods (Fig. 8j), associated with more wet/temperate conditions (SU 16 to 7; Fig. 8). The stratigraphy of these two Sub-ensembles corresponds to an inversed erosional stratigraphy. The lower part of the sequence (SU 15 to 10) corresponds to the erosion of fine sediments and ancient soils in the watershed. Indeed, dispersed reddish clay pedorelicts in the deposits (Brewer, 1964; Fig. 4a) suggest the erosion of red soils, which could have formed during a previous stable temperate period, which could correspond to milder interstadials of the MIS5. Above (SU7), coarser deposits correspond to the erosion of the exposed bedrock in the watershed. This specific 'inversed' sequence has already been attested over the southeastern France Mediterranean region and interpreted as evidence of climatic degradation during prominent climatic transitions (Dubar, 1995, 1987, 1983).

Towards the SU16, palynological data indicate warmer conditions with the appearance of *Quercus liex*, *Olea europea*, and *Fraxinus*, the increase in *Juniperus t.* and *Chicorideae*, and
the decline of *Pinus sylvestris* (Fig. 8h; Lopez-Saez et al., 1998). This follows the substantial
increase in semi-forest malacological taxa and the decrease in δ¹³C (Phase-IId, Audiard et al.,
2018; Fig. 8g, 8i). Interestingly, one temporary event identified in SU9/SU8 seems to record a
short-term hydro-climatic degradation. Indeed, SU8 corresponds to a small stream flow deposit
combined with a rapid decrease in semi-forested malacological taxa. These short-term events
were also recorded in the high δ¹³C values in charcoal (isotopic Phase-IVa; Audiard et al., 2018;
Fig. 8g), with cold and dry conditions in SU 9 and higher humidity in SU 8. Relatively to Sub-
Ensemble I and the Upper ensemble, however, conditions remain more humid. These
sediments are sealed by coarse fluvial-torrential deposits (SU7), marking the end of this phase.
Dates range between ~86 ka and 70 ka (Fig. 8e; Table 1).

517

5.1.3 – Aeolian deposits and cold/dry conditions

The Upper Ensemble (SU5 to SU2) records a substantial sedimentological and
environmental shift represented by: a) the appearance of a loess sequence characterized by an
allochthonous well-sorted mineral assemblage (Fig. 8j, k, l); b) the re-emergence of discrete
freeze-thaw features without prominent soil displacement (Fig. 8j); c) the reduction of
pinewood and the development of shrubby riparian vegetation resistant to cold (Fig. 8f; Théry-
Parisot and Texier, 2006); d) the reduction of semi-forested malacological taxa (Fig. 8i); e) and
the highest values of δ¹³C in charcoal, suggesting a more rigorous climate (Fig. 8g; Audiard et
al., 2019). This aeolian deposition began around 64.5 ± 9.2 ka (Fig. 8e; Table 1), documenting
the installation of glacial and peri-glacial conditions in the region. While the lower part of the
ensemble (SU5) indicates typical loess deposition, the presence of clay aggregates from the
SU4 (Fig. 8j) indicates the reworking of this original aeolian material and the formation of loess-
like sediments (Cremaschi, 1990) (Fig. 7a). Aeolian inputs into and at the southern margin of the Luberon Massif (Fig. 1) could be related to the influence of the Mistral wind regime from the Rhone valley. These hydrosedimentary and palaeoenvironmental conditions are typical of cold and dry environments with low water supply. However, at the end of the aeolian deposition (SU3 and 2), the lack of freeze-thaw pedo-facies with strong CaCO₃ secondary concentrations could suggest a slight warming trend (Courty and Vallverdu, 2001).

536

537

## 5.2 – La Combette sequence in a local-to-regional MIS5-MIS4 climatic transition

539

The combination of pedo-sedimentary and palaeoecological data from the La Combette Sequence allows us to reconstruct local environmental conditions (Fig. 8). The study of Sub-ensembles I, II, and III, indicate alternating warm and cold conditions supported by moderate to a high water supply. Based on new luminescence ages, these conditions are signatures of the hydro-climatic instability of the most recent sub-stages of the Last Interglacial period, between ~90 ka to ~70 ka.

In order to discuss the representativeness of our results at a regional scale, we compared our multiproxy observations with a) a close loess-palaeosol sequence recently investigated by Bosq et al. (2020b) in the Rhône valley (Fig. 8d); b) two palynological series from the septentrional part of the Rhône basin covering the same period (Fig. 8c; La Grande Pile, Les Echets; Faquette et al., 1999; Klotz et al., 2004; Helmens 2014; Fig. 1); c) the MD99-2348 core record from the Rhône deep delta (Fig. 8a, 8b; Sierro et al., 2009)

552
553 5.2.1 – The Last Late Interglacial period (~90 - ~70 ka)

554

555 The hydrological and palaeoenvironmental signatures recorded at the base of La
556 Combette sequence (Sub-ensemble-I; see 5.1.2), typical of fresh/humid (SU19) to colder (SU18-
557 17) environments, can be correlated to the hydro-climatic variations recorded in the
558 continuous regional archives. Indeed, during the end of MIS5, hydro-climate reconstruction
559 models at La Grande Pile (Fauquette et al. 1999) indicate low but regular precipitation (~500
560 mm/yr; Fig 8c) and low temperatures. In the Rhône deep delta, this same period is
561 characterized by a relative percentage of temperate/warm foraminifera and low terrigenous
562 inputs (Fig. 8a, 8b; Sierro et al., 2009). We put forward the hypothesis that the lower part of
563 the La Combette sequence belongs to one of the last cold sub-stages at the beginning of the
564 climatic degradation at the end of the MIS5-early MIS4. During this cold period, the rock shelter
565 was highly frequented by Neanderthals as a specialized hunting spot for several expeditions
566 (Texier et al., 2003).

567 From Sub-ensemble II, a shift of the hydrological regime has been recorded at La
568 Combette with the stepwise increase of fluvial inputs. Regionally, after the cold and relatively
569 low-rainfall period, the Interglacial sub-stage 5.1 (~85 - ~73 ka; Fig. 8) is characterized by higher
570 precipitation values (~800 mm/yr) and temperatures at La Grande Pile (Fauquette et al., 1999;
571 Fig. 8c). In the deep Rhône delta, the gradual increase in temperate/warm foraminiferal species
572 and high δ¹⁸O values on G. *bulloides* confirms the installation of milder conditions (Sierro et al.,
573 2009; Fig. 8a). Sedimentologically, from the same Rhône delta archive, a sandy layer (Fig. 8b)
574 also marks this sub-stage, reflecting the reactivation of the Rhône hydro-system and the
575 landward migration of the coastline (Sierro et al., 2009). Chronologically, this coarser sandy
event corresponds to the fluvial-torrential aggradation of the La Combette sequence (Sub-ensemble-II), generally ranged between ~86 ka and ~70 ka (Table 1; Fig. 8). Interestingly, these fluvial deposits contain markers of soil erosion (pedorelicts; Brewer, 1964; Fig. 4), suggesting an ancient soil cover (Interglacial soils) in the watershed of La Combette. In the Rhône watershed, evidence of Bwk red soil pedocomplexes at the Collias sequence was dated between 82.8 ± 7.2 ka and 87.1 ± 6.5 ka (Fig. 8d; Bosq et al., 2020b). There is some coherence in suggesting that these events (hydro-system fluvial reactivation and soil erosion) correspond to more humid conditions at the end of the MIS5 recorded regionally. Over the whole Mediterranean region, several records attested an increase of alluvial activity during this period (Macklin and Woodward, 2009). Indeed, the Last Interglacial – Glacial transition has trigged some significant landscape transformations around the Mediterranean, mainly corresponding to an increase of slope erosion and valley floor aggradation (Macklin and Woodward, 2009).

At La Combette, this humid interval is temporarily interrupted by a short-term episode characterized by reduced fluvial activity, colder environmental conditions, and reoccupation of the shelter (archaeological layer E, SU8; 80.1 ± 6.4 ka; Fig. 8d). This event seems to be absent in continuous continental/marine archives (Figs. 8a, 8b, 8c), underlining the relevance of terrestrial sequences for local to regional palaeoenvironmental reconstructions. Finally, the resumption of fluvial/torrential aggradation (SU7) marks the end of this climatic phase.

In summary, this warmer period recorded at La Combette likely corresponds to the last humid pulses of the MIS5. However, it can even include slight humid oscillations attested at the beginning of the MIS4, until ~70 ka (ex: Ognon complex; Fauquette et al., 1999; Helmens, 2014). However, the low resolution of luminescence ages, as well as the possible occurrence of erosive
598

processes between fluvial events, does not allow us to propose a precise correlation to regional

599

short-term humid oscillations which characterized the end of the MIS5/beginning of MIS4.

600

601

## 5.2.2 – The Early Glacial period (~70–~50 ka)

602

603

At La Combette, the first loess deposits have been dated from 66.1 ± 5.4 ka (BDX16813,

604

SU4) in concomitance with steppe-like vegetation. In this cold and arid environment, traces of

605

Neanderthal occupation are scarce apart from archaeological layer D (Texier et al., 2003).

606

Following our results, the regional palaeoclimatological marine and continental records

607

show a rapid cooling since ~70 ka corresponding to the installation of Würmian glacial

608

conditions (Fig. 8): low δ¹⁸O values in *G. Bulloides*, the reduction of fluvial dynamics (Sierro et

609

al., 2009), the decrease in temperatures and precipitation (<500 mm/yr; La Grande Pile,

610

Fauquette et al., 1999) combined with the spread of steppic species indicate arid conditions

611

(Helmens, 2014). Interestingly, at La Combette, SU3 records a short-term, slightly humid

612

episode (runoff reworking of aeolian material), which possibly corresponds to local hydrological

613

variations. The complete filling of the rock shelter by aeolian deposition marks the end of the

614

sequence during the MIS3 at around 40 ka (cf. Kreutzer et al., 2021; their Fig. 7) with persistent

615

cold and dry climatic patterns until this period. The installation of MIS4-MIS3 loess deposits is

616

even attested in the Rhône valley at La Collias sequence, supporting our results (Fig. 8d; Bosq

617

et al., 2020b).

618

The interruption of the aeolian sediment supply and freeze–thaw processes in the upper

619

layers, accompanied by a marked increase of carbonate weathering, may suggest a slight

620

warming trend (Courty and Vallverdu, 2001). Accordingly, after ~50 ka more temperate
621

conditions were regionally dominant in the Luberon/Lower Durance area, as well as in the
Lower Rhône valley (Dubar, 2008; Ollivier et al., 2014, Bosq et al., 2020b), with the development
of red and brown soils, likely corresponding to the installation of the Moershoofd-Pile
Interstadial until ~40 ka.

622

623

624

625

626

6 – Conclusions

627

628

Sedimentological, micromorphological, isotopic (charcoal δ¹³C), and palaeo-ecological (palynology, anthracology, malacology) studies have been combined at the site of La Combette (Luberon massif, western Provence region, France) to provide a new palaeoenvironmental and palaeoclimatological evidence for the MIS5 – MIS4 transition. Our results reveal climatic trends consistent with regional ones, but local data provide new and relevant information:

629

630

631

632

633

1) The response to climate change during the last sub-stages of the MIS5 in the Luberon area is characterized by a strong environmental instability, with alternating wet and cold conditions until ~70 ka. The last phase of this period shows a reactivation of the hydrographic system with an increasing erosion, which likely corresponds to the end of the sub-stage MIS5.1 and the onset of the MIS4 (ex: Ognon complex).

634

635

636

637

638

2) An important accumulation of cryoturbated loess deposits marks the installation of the glacial period at La Combette. Combined with palaeobotanical data, our results confirm the arid and cold character of the MIS4 and refine the chronology of the loess deposition in the Provence region.

639

640

641

642

Our results provide new data on the palaeoclimatic context of the Neanderthal settlements in the South of France during the Last Interglacial – Glacial transition, showing the

643
644

evidence of climatic deterioration characterized by high hydrological and temperature

645

instability followed by cold and dry conditions. They also highlight the necessity to improve the

646

multidisciplinary studies on known continental sequences to constrain further the

647

environmental context of Palaeolithic settlements facing prominent hydro-climatic disruptions.

648

649

650

Acknowledgments

651

Fieldwork, analyses, and thin section fabrication were funded by the CNRS CEPAM-

652

UMR7264, with the logistic support of P.-J.Texier. We would like to thank L. Meignen and E.

653

Nicoud for their assistance in the field and valuable comments on the manuscript. Thank you

654

also to M. Zanti for his help and support for the grain-size analysis at GEOAZUR-UMR7329. The

655

LaScArBx financed the work of SK. LaScArBx is a research program supported by the ANR (ANR-

656

10-LABX-52).

657

658

659
660 References

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665 pubescens Willd. du Montpelliérais. Premiers résultats. Malacologia 1, 483–488.

666 Arnaud-Fassetta, G., 1998. Dynamiques fluviales holocènes dans le delta du rhône (thesis). Aix-

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669 taxonomic and isotopic approaches in charcoal analyses to reveal past climates. New

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Tables

<table><caption>Table 1: Equivalent doses, environmental dose rates and luminescence ages on quartz after (Kreutzer et al., 2021).</caption><thead><tr><th>SAMPLE</th><th>Depth<br>North section</th><th>SU</th><th>Archaeological<br>layer</th><th>D̂<sub>total</sub><br>[Gy kyr<sup>-1</sup>]</th><th>D<sub>e</sub><br>[Gy]</th><th>Age<br>[ka]</th></tr></thead><tbody><tr><td>BDX16811</td><td>130 cm</td><td>2</td><td>A</td><td>2.0 ± 0.1</td><td>114.9 ± 7.8</td><td>57.4 ± 5.4</td></tr><tr><td>BDX16812</td><td>210 cm</td><td>2</td><td>B/C</td><td>1.8 ± 0.1</td><td>119.5 ± 8.9</td><td>66.5 ± 6.8</td></tr><tr><td>BDX16813</td><td>330 cm</td><td>4</td><td>D</td><td>1.8 ± 0.1</td><td>117.2 ± 4.8</td><td>66.1 ± 5.4</td></tr><tr><td>BDX16814</td><td>440 cm</td><td>7</td><td>/</td><td>1.9 ± 0.1</td><td>125.2 ± 15.6</td><td>64.5 ± 9.2</td></tr><tr><td>BDX16815</td><td>510 cm</td><td>8</td><td>E</td><td>1.5 ± 0.1</td><td>118.8 ± 3.5</td><td>80.1 ± 6.4</td></tr><tr><td>BDX16816</td><td>520 cm</td><td>17</td><td>F/G</td><td>1.8 ± 0.1</td><td>126.4 ± 3.9</td><td>71.9 ± 5.5</td></tr></tbody></table>

918

919

920

<table><thead><tr><th>SU</th><th>Archaeological layer</th><th>Depth<br>(North section, cm)</th><th>Pomatias elegans</th><th>Granaria variabilis</th><th>Chilostoma squamatimum</th><th>Clausilia Parvula</th><th>Abida secale</th><th>Trochoidea Geyeri</th><th>Cepaea sp.</th><th>Vallonia costata</th><th>Eumphalia strigella</th><th>Oxychilus</th><th>Limacelles</th></tr></thead><tbody><tr><td>2</td><td>B/C</td><td>225-230</td><td></td><td></td><td>1</td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>2</td><td>B/C</td><td>230-235</td><td></td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>2</td><td>B/C</td><td>235-240</td><td></td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>2</td></tr><tr><td>2</td><td>B/C</td><td>240-245</td><td></td><td></td><td>1</td><td>1</td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>4</td><td>D</td><td>330-335</td><td></td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>4</td><td>D</td><td>335-340</td><td>1</td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>
<table><caption>Table 2: Malacological determination of archaeological layers of La Combette</caption><tr><td>5</td><td>D</td><td>340-345</td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>5</td><td>D</td><td>345-350</td><td></td><td>1</td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>5</td><td>D</td><td>350-355</td><td></td><td>1</td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>1</td></tr><tr><td>7</td><td></td><td>410-415</td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>7</td><td></td><td>415-420</td><td></td><td></td><td>1</td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>8</td><td>E</td><td>435-440</td><td></td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>8</td><td>E</td><td>440-445</td><td></td><td></td><td>3</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>8</td><td>E</td><td>445-450</td><td></td><td></td><td>3</td><td></td><td>2</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>8</td><td>E</td><td>450-455</td><td></td><td></td><td>2</td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>1</td><td></td></tr><tr><td>8</td><td>E</td><td>455-460</td><td></td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>1</td><td></td><td></td></tr><tr><td>17</td><td>F/G</td><td>490-495</td><td></td><td>1</td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>17</td><td>F/G</td><td>495-500</td><td></td><td>1</td><td>2</td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>17</td><td>F/G</td><td>500-505</td><td></td><td>1</td><td></td><td>3</td><td></td><td></td><td>1</td><td></td><td></td><td></td><td>1</td><td></td><td></td><td></td></tr><tr><td>18</td><td>F/G</td><td>505-510</td><td></td><td>1</td><td></td><td>1</td><td>1</td><td></td><td></td><td>1</td><td></td><td></td><td>1</td><td></td><td></td><td></td></tr><tr><td>Tot</td><td></td><td></td><td></td><td>6</td><td>4</td><td>26</td><td>6</td><td>4</td><td>3</td><td>1</td><td>2</td><td>1</td><td>1</td><td>3</td><td></td><td></td></tr></table>

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923 Captions
<figure><img src="image_2.png" /></figure>
925 **Figure 1: a)** Geographic location of the regional study area and other important regional palaeoclimate records (white stars): 'La Grande Pile' (Fauquette et al., 1999; Helmens, 2014; Seret et al., 1990; Woillard and Mook, 1982), 'Les Echets' (Beaulieu and Reille, 1984; de Beaulieu and Reille, 1989), MD99-2348 core (Sierro et al., 2009); **b)** 'La Combette' rock shelter (red star), the Collias sequence (black star; Bosq et al., 2020b), the other MIS5/4 sequences discussed in this study (reversed red triangles), the main towns (black squares); the aeolian sand and loess deposits (brown and green dots; Bertran et al., 2016; Bosq et al., 2020, 2018), the Luberon Massif area (brown dotted line), the Russian and Würmian (red and blue dotted lines respectively) glacier lobe extents (Buencristiani and Campy, 2011; Cossart et al., 2011, 2008).

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<figure><img src="image_3.png" /><figcaption>Figure 2: a) Picture of La Combette stream landscape with the rock shelter location; b) La Combette sequence picture with the location of SU and sampled sections.</figcaption></figure>

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<figure><img src="image_4.png" /><figcaption>**Figure 3:** a) Upper and b) Lower sedimentary Ensembles stratigraphy (SU and archaeological layers), with location of luminescence samples (orange squares), micromorphological (yellow squares), sedimentological samples (red dots) and magnetic susceptibility results (blue curve-line).</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>**Figure 4:** a) sediment picture, thin section n°7 scan (PPL) with indicated the red soil pedorelicts (black arrows) and grain size Gaussian distribution of MSF-1.a and MSF-1.b facies; b) Microphotography of the MSF-2.b facies (PPL); c) Microphotography of the MSF-2.c facies (PPL); d) Microphotography of the MSF-3.a facies (XPL); e) Microphotography of the MSF-3.b facies (PPL).</figcaption></figure>
<figure><img src="image_6.png" /></figure>

**Figure 5:** Microphotographs of pedoclimatic markers belonging to the MPF-2a and MPF-2b facies a) Simple ice segregation MPF-2.a facies in a runoff deposit (MSF-2.a; PPL); b) simple ice segregation MPF-2.a facies in a silty-sandy rock shelter filling (MSF-3.b facies PPL); c) MPF-2.b facies: well developed 'banded fabric': (ss) sorted sand grains with inverted grading, (sc) layered silt cappings, (ag) lenticular aggregate, after Van Vliet-Lanoë (2010); d) MPF-2.b facies: 'bended fabric' from SU3 (thin section n°11; PPL).
<figure><img src="image_7.png" /></figure>

**Figure 6:** : Microphotographs of pedoclimatic markers belonging to the MPF-2c facies a) MPF-2.c facies: black arrows indicate the ice blade fine-sand-filling and the settling with displacement microstructure (PPL); b) MPF-2.c facies: black arrows indicate the strial b-fabric between two molassic coarse fragments (XPL); c) MPF-2.c facies: black arrows indicate the fissured and rotated clayey-silty cappings in a well-developed granular microstructure (PPL); d) MPF-2.c facies: black arrows indicate the mechanical fragmented molassic very coarse sand grain (PPL).
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<figure><img src="image_8.png" /></figure>

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Figure 7: **a)** scan of thin section n°12 (SU3; PPL), alternating silty-clay runoff (MSF-2.a, micro-SU 2, 4) and laminated loess colluvium (MSF-2.b, micro-US1, 3, 5); **a.1)** Microphotograph of a fragmented clay-silty crust - MSF-2.b facies (PPL); **a.2)** Microphotograph of facies MSF-2.a and MPF-2a (PPL); **a.3)** Microphotograph of an in situ fragmented nodule - MSF-2.b facies. **b)** scan of thin section n° 16 (SU2; PPL): **b.1)** Microphotograph of a fragmented clay crust-MSF-2.c facies (PPL); **b.2)** Microphotograph of a micritic crystallite infillings in a bioturbation channel (MPF-1.a and MPF-3.a; XPL).

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Regional Palaeoclimatological Record
and proposed correlations

<figure><img src="image_9.png" /></figure>

La Combette Palaeoenvironmental studies

<figure><img src="image_10.png" /></figure>
**Figure 8:** La Combette results compared to the regional continuous palaeoclimatic records: a) $\delta^{18}$O on G. bulloides and b) fine sand (%) curves from the MD99-2348 core (Sierro et al., 2009); c) annual precipitations (mm/a) based on the sequence of La Grande Pile (Fauquette et al., 1999); d) Stratigraphy of the Collias section (Bosq et al., 2020b), with the location of the luminescence samples (black stars); e) stratigraphy of La Combette section with the location of luminescence samples (red stars); f) anthracological results (Théry-Parisot and Texier, 2006; Audiard et al., 2019); g) $\delta^{13}$C on charcoal results (Audiard et al., 2019); h) palynological results on the La Combette sequence (Lopéz-Saéz et al., 1998); i) malacological results; j) micromorphological facies defined along the sequence of La Combette (this manuscript); k) heavy minerals analysis results (this manuscript); l) grain size analysis results (this manuscript); m) calcium carbonate concentration analysis results (this manuscript).