Ting Kong

Alina Tudryn

Elisabeth Gibert-Brunet

Piotr Tucholka

Seyed-Hani Motavalli-Anbaran

Hesam Ahmady-Birgani

Mohammad Lankarani

Serge Miska

Aurélie Noret

Olivier Dufaure

30,000 Years of the southwestern Lake Urmia (Iran) paleoenvironmental evolution inferred from mineralogical indicators from lake and watershed sediments

Keywords: Lake Urmia, Late Quaternary palaeoenvironments, Water level change, Carbonates, Clay minerals, 14 C dating

HAL is

Introduction

Located in Northwestern Iran, Lake Urmia is a natural habitat of brine shrimp Artemia urmiana and the salinity of lake water commonly ranges from 120 to 280 g.L -1 , regarded as a UNESCO biosphere reserve and a Ramsar wetland [START_REF] Asem | Drought in Urmia Lake, the Largest Natural Habitat of Brine Shrimp Artemia[END_REF]. However, since increased anthropic activities inside the lake basin (brine shrimp farming) and its watershed area (agriculture) in the mid-1990s, Lake Urmia dropped by 7 m, that led to drastic reduction in lake surface area, ground-and lake water salinization, desertification and dust storms threatening health conditions of millions of people at a regional scale [START_REF] Alipour | Hydrogeochemistry of Seasonal Variation of Urmia Salt Lake, Iran[END_REF][START_REF] Pengra | Sioux Falls[END_REF][START_REF] Ghalibaf | Development and Environment in Urmia Lake of Iran[END_REF][START_REF] Aghakouchak | Aral Sea Syndrome Desiccates Lake Urmia: Call for Action[END_REF][START_REF] Ahmady-Birgani | Mineralogy and Geochemistry of Atmospheric Particulates in Western Iran[END_REF][START_REF] Ahmady-Birgani | On the Chemical Nature of Wet Deposition over a Major Desiccated Lake: Case Study for Lake Urmia Basin[END_REF]. The decline of the lake water volume has already concentrated the original salinity even up to 380 g.L -1 in many locations [START_REF] Sharifi | The Vanishing of Urmia Lake: A Geolimnological Perspective on the Hydrological Imbalance of the World's Second Largest Hypersaline Lake[END_REF]. The water-level drop has been attributed to anthropogenic causes such as the construction of many dams on rivers feeding the lake, abusive groundwater abstraction, and to rainfall declining [START_REF] Alipour | Hydrogeochemistry of Seasonal Variation of Urmia Salt Lake, Iran[END_REF][START_REF] Jalali | Holocene Climate Variability in the North-Western Mediterranean Sea (Gulf of Lions)[END_REF], although the exact impact of both factors is not yet well identified. Even if the anthropogenic causes can be estimated and modified, the past evolution of the lake basin that may help to better understand the ongoing and future lakes evolutions is not well known through some data already existed. [START_REF] Asem | Drought in Urmia Lake, the Largest Natural Habitat of Brine Shrimp Artemia[END_REF] mentioned historical documents indicating that Lake Urmia experienced a severe drought in the beginning of the 1800 's with a maximum lake depth of 75 cm and an east-west road created across the lakebed. Existing studies of Late Quaternary sediments from the lake including sedimentology, geochemistry and pollen, are various but (i) concern only the most recent Holocene period about the last 2550 years [START_REF] Talebi | The Late-Holocene Climate Change, Vegetation Dynamics, Lake-Level Changes and Anthropogenic Impacts in the Lake Urmia Region[END_REF] or surface sediments [START_REF] Erfan | Clay Mineralogy and Sediment Grain-Size Variations as Climatic Signals in Southern Part of Urmia Lake Cores[END_REF][START_REF] Sharifi | The Vanishing of Urmia Lake: A Geolimnological Perspective on the Hydrological Imbalance of the World's Second Largest Hypersaline Lake[END_REF], (ii) focus on the whole Holocene but with a low temporal resolution [START_REF] Bottema | A Late Quaternary Pollen Diagram from Lake Urmia (Northwestern Iran)[END_REF][START_REF] Kelts | Holocene Sedimentology of Hypersaline Lake Urmia, Northwestern Iran. %J Palaeogeography[END_REF]), (iii) on Late Pleistocene and the Holocene without precise chronology (Mirzapour et al., 2021a;Mirzapour et al., 2021b), or (iv) cover large time scale (200 kyr) but again with poor or missing information on Late Pleistocene and the Holocene (Djamali et al., 2008a;Djamali et al., 2008b;[START_REF] Stevens | Hydroclimatic Variations over the Last Two Glacial/Interglacial Cycles at Lake Urmia, Iran[END_REF]. Whatever their chronological resolution, these studies indicate the highest amplitude of lake-level variations at a glacial-interglacial time scale with a dry open mountain steppe dominating during the glacial periods and a steppe-forest environment during interglacials. Over the Holocene, saline deposition seems almost continuous with clear water level changes but no visible total desiccation of the lake. In addition, the vegetation reached its maximum destruction due to increasing human impact during the last centuries.

The present study aims to accurately decipher the pattern and trends of environmental change in the southwestern part of the lake basin over 30 kyr. Preliminary results on Lake Urmia sedimentary cores were published by our team [START_REF] Tudryn | Late Quaternary Environmental Changes of Lake Urmia Basin (Nw Iran) Inferred from Sedimentological and Magnetic Records[END_REF], proposing the lake level fluctuations but with an overall unclear timescale. In order to reliably precise the chronology and the related environment phases, we performed mineralogical studies both on the core sediments and on those of the Shahr Chay River catchment, which is the main provider of detrital input to the coring site. Based on X-ray diffraction analyses on bulk sediment samples, we identified the principal silicates, carbonates and evaporites, on clayish fraction -clay minerals, and we analyzed sediment grain size distribution. The chronology has been established on 13 14 C dating of organic matter and authigenic carbonates.

Study area

Lake Urmia basin (35.5-38.5° N and 44-48° E) is part of the tectonic crush zone between the colliding Arabian and Eurasian plates [START_REF] Mckenzie | The East Anatolian Fault: A Major Structure in Eastern Turkey[END_REF]) (Fig. 1a). Based on Sharifi and co-authors (2018), the lacustrine basin is divided into two sub-basins: the deep northern basin and the shallow southern basin with an average depth of 10 and 2 m respectively. Between two basins, an east-west dike-type highway that stretches 15 km across the center of the lake has been constructed. The whole lake has 13 perennial and seasonal tributaries, but the main water inflow to the southwestern lake area close to the coring site originates from Shahr Chay River that is also named Shahi Chay River [START_REF] Sharifi | The Vanishing of Urmia Lake: A Geolimnological Perspective on the Hydrological Imbalance of the World's Second Largest Hypersaline Lake[END_REF]. Sharifi and co-authors (2018) also report the annual mean river discharge and the mean catchment area of the major tributaries. Lake Urmia displays a unique, highly valuable biodiversity that favors a highly productive agriculture and brine shrimp farming, and makes the region as one of the most important economic poles of Iran.

The geology of Lake Urmia catchment is quite diverse, ranging from Precambrian metamorphic complexes to Quaternary mud deposits (Fig. 1b). In the east and northeast parts of the catchment, volcanic and volcanosedimentary formations dominate while intrusive rocks prevail over the rest of the catchment, with mainly metamorphic rocky outcrops in the Zagros to the west, complemented in the south by dolomites, sandstones, quartz and volcanic rocks from the Infracambrian. Carbonate rocks are found in south and western parts of the basin while evaporative sedimentary units are only found northeast of the watershed.

Owing to the effects of local topography, the Urmia basin climate is mainly controlled by the surrounding mountains, and thus the semi-arid continental climate is characterized by rather large variations in temperature and precipitation. According to the Urmia meteorological station (west of Urmia Lake at 1,313 m a.s.l.), the temperature was below 10 ℃ in winter and up to 40 ℃ in summer, and the mean annual precipitation was recorded as about 300 mm [START_REF] Kelts | Holocene Sedimentology of Hypersaline Lake Urmia, Northwestern Iran. %J Palaeogeography[END_REF][START_REF] Sharifi | The Vanishing of Urmia Lake: A Geolimnological Perspective on the Hydrological Imbalance of the World's Second Largest Hypersaline Lake[END_REF]. Whereas a steady decline is registered since several years, the most recent satellite altimeter data indicating a drop of approximately 7 m over the last 20 years, with a lake level ranging from 1277.5 m in 1999 to 1270.85 m in 2019 [START_REF] Ahmady-Birgani | On the Chemical Nature of Wet Deposition over a Major Desiccated Lake: Case Study for Lake Urmia Basin[END_REF]. Because the southern part of the lake (south of the dike-type highway) is relatively shallow, the water level decline exacerbates the dramatic decline of the lake surface area.

According to [START_REF] Ahmady-Birgani | On the Chemical Nature of Wet Deposition over a Major Desiccated Lake: Case Study for Lake Urmia Basin[END_REF], the lake surface decreases all the time and from 1999 to 2019, the lake even lost half of its surface area (5000 km 2 in 1999 vs 2400 km 2 in 2019) and had less of almost 20 bm 3 of its water volume.

Materials and methods

Material collection

Lake sediment sampling

In September 2017, two sediment cores, i.e. Golman 6 (8.0 m long) and Golman 7 (12.5 m long), have been collected from the SW part of recently dried out part of the lake, near the city of Urmia (Fig. 1c, Table 1).

The cores have been taken in close proximity to each other, with the mechanic corer and a borehole casing at a distance from today's shoreline allowing safe use of the corer. Details of sampling and coring conditions are given in [START_REF] Tudryn | Late Quaternary Environmental Changes of Lake Urmia Basin (Nw Iran) Inferred from Sedimentological and Magnetic Records[END_REF]. The coring was stopped when pressurized water with mud and gas with an intense H2S odor rose up from the Golman 7 borehole to the lake surface and when gas with the same odor rose up from the Golman 6 borehole.

Due to the presence of interbedded captured water (either residual water from the sediment or ancient lake water trapped within the deposits), the 4.2 to 8.65 m section of Golman 7 core was too humid to be retrieved by the corer, leading to an empty section for this depth interval. Moreover, consequently to the soft and humid lacustrine ground at the core site, the first section of Golman 6 core taken from 0 m to 4.0 m depth, was compacted and only collected as 3.15-4.0 m depth. Although the two cores Golman 6 and Golman 7 present these inconsistencies, they represent together a continuous sequence as a composite core (Fig. 2a, b, c).

Catchment sediment sampling

In June 2021, eight geological samples have been collected from the catchment area of the Shahr Chay River that is the major supplier of detrital material into the lake at the coring location. These 8 samples have been selected according to the main geological formations of the river catchment (Table 1, Fig. 1c).

Accordingly, samples represent the following formations: 1-pyroclastic and claystone with vertebrate fauna remains, andesitic to basaltic volcanics; 2 and 7-high level piedmont fan and valley terraces deposits; 3, 4 and 5-red beds composed of red conglomerate, sandstone, marl, gypsiferous marl; 6 -phyllite, slate and meta-sandstone (Hamadan phyllites); 8 -dark gray medium-bedded to massive limestone.

Methods

Grain size and clay mineralogy

Grain size and clay mineral analyses have been performed at the GEOPS laboratory, Paris-Saclay University (Orsay, France) on 116 and 84 samples taken at every 5 cm depth intervals from cores Golman 7 and Golman 6 respectively. For each sample, about 5-10 g of air-dried, disaggregated sediment was pretreated in a 33% hydrogen peroxide (H2O2) bath to remove organic matter and then with a 20% acetic acid solution (CH3COOH) to remove carbonates. After that, the samples were rinsed with deionized water in order to obtain neutral pH. These organic-free and carbonate-free samples have then been used for grain size distribution and for clay mineral analyses. The grain-size distribution was carried out on samples dispersed by ultrasonic vibrator for 3 min before analysis using a Malvern Mastersizer 2000 laser device.

Clay minerals have been identified by X-ray diffraction (XRD) on oriented mounts of clay sized (< 2 µm) particles with a PANalytical diffractometer, following the laboratory routine of the GEOPS laboratory.

Three XRD runs were made, after a specific chemical treatment of air-drying, ethylene glycol solute leaching for 12 h, and heating at 500 °C for 2 h and return back to normal temperature (Holtzapffel, 1985).

The identification of clay minerals peaks was made mainly according to the position of the (001) series of basal reflections. Semi-quantitative estimates of peak areas of the basal reflections for the main clay mineral groups of smectite (including mixed-layers) (16.9 Å), illite (10 Å), kaolinite (3.57 Å), chlorite (3.54 Å) and kaolinite + chlorite (7.16 Å) were carried out on the glycolated curve using the MacDiff software (Petchick, 2000). Relative proportions of kaolinite and chlorite were determined based on the ratio 3.57/3.54 Å of the peak areas. Evaluation of each clay mineral has an accuracy of ca 5%. Furthermore, the illite chemistry index was estimated using the ratio of the integrated 5 Å and 10 Å illite peak areas on the XRD diffractograms [START_REF] Esquevin | Influence De La Composition Chimique Des Illites Sur Leur Cristallinité[END_REF]. The illite chemistry index value > 0.4 represents the Al-rich illites, while a value < 0.4 represents Fe-and Mg-rich illites [START_REF] Diekmann | Clay Mineral Fluctuations in Late Quaternary Sediments of the Southeastern South Atlantic: Implications for Past Changes of Deep Water Advection[END_REF][START_REF] Ehrmann | Clay Minerals in Cenozoic Sediments Off Cape Roberts (Mcmurdo Sound, Antarctica) Reveal Palaeoclimatic History[END_REF]. Additionally, the illite and smectite crystallinities were separately obtained from the full width half maximum (FWHM) of the 10 Å and 16.9 Å peak respectively. According to [START_REF] Ehrmann | Clay Minerals in Cenozoic Sediments Off Cape Roberts (Mcmurdo Sound, Antarctica) Reveal Palaeoclimatic History[END_REF], this parameter indicates the state of illite crystallization as (i) very well crystallized (< 0.4), well crystallized (0.4-0.6), moderately crystallized (0.6-0.8), poorly crystallized (>0.8), and of (ii) smectite as well crystallized (<1.5), moderately crystallized (1.5-2.0), and poorly crystallized (>2.0) [START_REF] Ehrmann | Clay Minerals in Cenozoic Sediments Off Cape Roberts (Mcmurdo Sound, Antarctica) Reveal Palaeoclimatic History[END_REF].

Bulk sediment mineralogy

Identification of total mineralogical components of the whole sediment has been performed by XRD at GEOPS laboratory by XRD analyses of 52 samples with an X'Pert Pro PANalytical diffractometer, Cu-K source, 2ϴ range 5°-80°, 4 h runs. The identification of mineralogical phases was conducted using the PANalytical HighScore software with crystallography open database and ICDD PDF-4/Minerals database following the laboratory routine at GEOPS laboratory. The semi quantification of minerals was determined according to the area of main peak on quartz (3.34 Å). In addition, specific carbonates have been identified through analyzes during 45 minutes with 2ϴ range 24°-33°. Then the semi-quantification of the carbonates was obtained by normalizing the areas of the diffraction peaks of identified minerals (aragonite 3.39 Å; calcite 3.03 Å; dolomite 2.88 Å) with respect to the percentage of areas coming from an equi-mass mixture of carbonates, then setting the ratio of the normalized area of each carbonate to the sum of the standardized areas. Associated to the relative percentages of these carbonates, carbonate crystallinity was measured on the main peak through full width half maximum (FWHM). This index determined by measuring the enlargement of the carbonate peak likely reflects the authigeny of the crystal. Indeed, according to [START_REF] Fontes | Stable Isotope and Radiocarbon Balances of Two Tibetan Lakes[END_REF][START_REF] Fontes | Holocene Environmental Changes in Lake Bangong Basin (Western Tibet). Part 1: Chronology and Stable Isotopes of Carbonates of a Holocene Lacustrine Core[END_REF], detrital, well crystallized carbonates display thin shape of the peak and thus low values of crystallinity index while for authigenic carbonates that are less well crystallized, this index is high [START_REF] Fontes | Stable Isotope and Radiocarbon Balances of Two Tibetan Lakes[END_REF][START_REF] Fontes | Holocene Environmental Changes in Lake Bangong Basin (Western Tibet). Part 1: Chronology and Stable Isotopes of Carbonates of a Holocene Lacustrine Core[END_REF].

Radiocarbon chronology

The 14 C time-scale has been defined through 13 AMS dating both on (i) organic fractions including diffused organic matter and hand-picked charcoal, and (ii) carbonates fractions on inorganic fractions and on handpicked shrimp's fecal pellets when existing.

Each organic fraction was submitted to the standard chemical protocol for AMS analyses: 3 successive hydrochloric acid/sodium hydroxide/hydrochloric acid baths, followed by several rinses with deionized water up to neutral pH, and gently drying-up at 60 °C overnight. The CO2 gas was obtained (i) for organic samples by burning at 860 °C for 30 min, under vacuum, in presence of a mixing of copper(II)-oxide/copper(III)-oxide and silver thread, and (ii) for carbonates, by an H3PO4 acid attack under vacuum during one night in a thermostatic bath. Then, AMS-14 C targets were obtained by graphitization of the CO2 gas on powdered iron with hydrogen at 650 °C for 100 min, and graphite compression under analytical plots. Aliquot of the CO2 gas was then used for associated 13 C measurement. Graphite sources were prepared in GEOPS laboratory, and counted by the accelerator mass spectrometer at LSCE laboratory (ECHoMICADAS facility, France).

Analytical uncertainties, including laboratory errors, are ± 0.1‰ for δ 13 C and between 0.5 and 0.8 pMC for 14 C activity. All the dates are converted to calendar ages according to the revised calibration program CALIB 8.2 (Execute Version 8.2 html 2020; Table 2) [START_REF] Reimer | Intcal13 and Marine13 Radiocarbon Age Calibration Curves 0-50[END_REF][START_REF] Reimer | The Intcal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0-55 Cal Kbp)[END_REF]Stuiver et al., 2021).

Results

Catchment area samples

The results of grain size, bulk sediment mineralogy and clay minerals analyses of 8 samples from the main geological formations are presented in Table 3. Grain size distribution indicates that the silt fraction predominates in all samples, ranging from 67.5 to 85.2%. In the silty fraction, coarse silt with 36.3 to 53.9% presents higher content than the fine one with 15.7 to 38.4% respectively; only sample 6 shows both two fractions in the same proportions. The second dominant fraction is sand ranging from 9.3 to 28.3%, while the clayish fraction remains at low contents, i.e. between 2.2 and 5.8%.

Considering bulk sediment samples, several groups of minerals are identified such as (i) carbonates (calcite and dolomite), (ii) silicates: quartz, mica (muscovite), feldspar (albite, orthoclase, anorthite), amphibole (hornblende), clays (chlorite, kaolinite, illite, smectite and some palygorskite), and (iii) oxides and hydroxides: rutile, magnetite and goethite. Among these minerals, the most frequent ones have been semiquantified (Table 3).

As a whole, calcite and quartz are predominant. Quartz varies between 7.3 and 55.8% and reaches the highest values (31.7 and 55.8%) in samples 2, 6 and 7. Calcite prevails in samples 1, 3, 4, 5 and 8, ranging from 53.9 to 79.3%, while it is absent in sample 6. Dolomite is only present in samples 1, 2, 3, 5 and 8, and varies between 5.8 and 18.5%. Low values of crystallinity index obtained for calcite and dolomite in all units where they occur (0.08-0.12) indicate that they are well crystallized [START_REF] Fontes | Stable Isotope and Radiocarbon Balances of Two Tibetan Lakes[END_REF][START_REF] Fontes | Holocene Environmental Changes in Lake Bangong Basin (Western Tibet). Part 1: Chronology and Stable Isotopes of Carbonates of a Holocene Lacustrine Core[END_REF].

In all samples, clays, mica and feldspars are in relatively low contents except sample 6, in which the high values are 19.1%, 29.8% and 19.3%, respectively. Further analysis of the clay assemblages in the claysized siliceous fraction, which allows more accurate estimates than in the bulk sediment, shows that smectite and illite are the most common (Table 3). Smectite is predominant in samples 1 and 7, with 58.2 and 72.7%, respectively. Meanwhile, the ratios of smectite/illite (S/I) in these two samples are more than 3. Illite prevails in samples 3,5,6 and 8, ranging from 42.4 to 52.0%, as a consequence of the S/I ratio much smaller than 1. In samples 2 and 4, smectite and illite display similar percentages with a S/I ratio about 1.

Kaolinite and chlorite reach lower values as a whole. Chlorite shows the same change pattern with illite and one can observe that chlorite contents are quite high reaching even to 31.9% in samples where illite dominates. Nevertheless, it is very low in sample 7. Kaolinite remains at about 10%, with however higher values for samples 5 and 8 (ca 18%) and lowest value for sample 7 (2.2%).

The illite chemistry index of all eight samples is less than 0.4 (Table 3), suggesting Fe-and Mg-rich illites as it was proposed by [START_REF] Diekmann | Clay Mineral Fluctuations in Late Quaternary Sediments of the Southeastern South Atlantic: Implications for Past Changes of Deep Water Advection[END_REF] and [START_REF] Ehrmann | Clay Minerals in Cenozoic Sediments Off Cape Roberts (Mcmurdo Sound, Antarctica) Reveal Palaeoclimatic History[END_REF]. In addition, smectite and illite crystallinities of these samples are ranging from 0.27 to 0.76 and from 0.17 to 0.30 respectively. Being less than 1.50 for smectite and less than 0.40 for illite, these values indicate well-crystallized clay minerals [START_REF] Diekmann | Clay Mineral Fluctuations in Late Quaternary Sediments of the Southeastern South Atlantic: Implications for Past Changes of Deep Water Advection[END_REF][START_REF] Ehrmann | Clay Minerals in Cenozoic Sediments Off Cape Roberts (Mcmurdo Sound, Antarctica) Reveal Palaeoclimatic History[END_REF].

Lake sediments 4.2.1. Lithology

The 8-m long Golman 6 core presents two major sedimentary sequences, under and upper the 4.52 m depth (Fig. 2a). In the lower part from 8.00 to 4.52 m depth, quite fine, grey silty and clayish sediments dominate while the above 4.52-4.23 m interval is composed of sandy and silty deposits. In the last section of the upper part in Golman 6 core has been compacted to the 4-3.15 m interval from 4-0 m during coring. The Golman 7 sequence is 12.5 m long and also divided into two major sequences separated by an empty interval due to missing sediment between 8.65-4.20 m (Fig. 2b). The lower part between 12.50 and 8.65 m depth is mainly composed of grey silts and clays while the above section from 4.20 m to the core top at 1.60 m depth encloses several lithological variations highlighted, similarly as in the Golman 6 core, by changes in the grain size, color and nature of the sediment.

The lacustrine sedimentation depicted in these two cores evidences the same lithological succession, although with slight differences in unit thicknesses. In order to better integrate and therefore interpret all the results as a whole set of data, a single stratigraphic sequence was reconstructed based on lithological changes as well as on carbonate contents and magnetic susceptibility [START_REF] Tudryn | Late Quaternary Environmental Changes of Lake Urmia Basin (Nw Iran) Inferred from Sedimentological and Magnetic Records[END_REF]. The composite sequence defined thus displays the complete Lake Urmia sedimentation from 12.50 m depth to the core top at 1.60 m depth with the following major lithological units (Fig. 2c).

The lower unit 1 between 12.50 and 4.52 m depth begins with sub-unit 1a, from the core base to 12.38 m depth, consisting in brownish sand followed by a dark grey, organic-rich black event at 12.48-12.43 m interval and then by grey silt above. From 12.38 to 4.52 m, the sub-unit 1b consists of grey silty/clayish deposits (Fig. 2d) containing some 1-mm thick sandy levels interbedded and an interval between 8.87-8.65 m marked by higher contents of silt and sand. Unit 2 presents a much more heterogeneous pattern with successive sub-sections as follows: (i) sub-unit 2a between 4.52 and 4.02 m depth consisting in brown sand and silt (Fig. 2e); (ii) sub-unit 2b from 4.02 to 3.85 m, made of homogeneous grey silts and clays; (iii) subunit 2c comprised between 3.85 and 3.73 m, containing grey and dark grey sand; (iv) sub-unit 2d at 3.73-2.87 m depth and formed by homogeneous grey clayish levels; (v) sub-unit 2e made of sandy and silty layers from 2.87 to 2.20 m depth (Fig. 2f), overlaying a 8-cm dark grey and black organic rich level, and (vi) sub-unit 2f that consists in grey sand from 2.20 to the core top at 1.60 m depth.

In addition, the two sub-units 2d and 2f contain lots of fecal pellets from the development of the brine shrimp Artemia urmiana in the lake (Fig. 2g-i). These pellets are white, sometimes dark, and they constitute almost 90% of many levels of sub-unit 2d (Fig. 2h). In the lower unit 1, fecal pellets are absent except for only few thin levels, in which some white pellets have been observed at 9.86 m and 10.92 m depth. These 50-200 μm, white fecal capsules of brine shrimp Artemia are considered as authigenic sedimentary component, although composed of a mixture of carbonates with minor amounts of siliclastic particles [START_REF] Kelts | Holocene Sedimentology of Hypersaline Lake Urmia, Northwestern Iran. %J Palaeogeography[END_REF][START_REF] Sharifi | The Vanishing of Urmia Lake: A Geolimnological Perspective on the Hydrological Imbalance of the World's Second Largest Hypersaline Lake[END_REF]. According to [START_REF] Kelts | Holocene Sedimentology of Hypersaline Lake Urmia, Northwestern Iran. %J Palaeogeography[END_REF], fecal pellets are composed of more than 80% aragonite in modern sediment beds, while when they are darker in color, it is suggested that fecal pellets are older reworked. According to the studies in Great Salt Lake, the presence of fecal pellets in the sediment indicates that Artemia thrives in the water salinity between 100 and 300 g.L - 1 but its tolerance of salinities can extend up to about 340 g.L -1 [START_REF] Post | A Procaryotic Intracellular Symbiont of the Great Salt Lake Brine Shrimp Artemia Salina[END_REF][START_REF] Sharifi | The Vanishing of Urmia Lake: A Geolimnological Perspective on the Hydrological Imbalance of the World's Second Largest Hypersaline Lake[END_REF].

For a water salinity lower than 100 g.L -1 , the decrease in the shrimps population is explained by increasing predators, while in a water salinity more than 300 g.L -1 , Artemia can hardly live [START_REF] Wurtsbaugh | Limnological Control of Brine Shrimp Population Dynamics and Cyst Production in the Great Salt Lake, Utah[END_REF]Agh et al., 2008;[START_REF] Esmaeili Dahesht | The Fluctuations of Physicochemical Factors and Phytoplankton Populations of Urmia Lake[END_REF]. In addition, when the lake water temperature is less than ca 3 °C, the shrimps are completely absent [START_REF] Wurtsbaugh | Limnological Control of Brine Shrimp Population Dynamics and Cyst Production in the Great Salt Lake, Utah[END_REF].

Grain-size distribution

The distribution patterns of major grain-size classes for the siliclastic fraction of Lake Urmia sediments are shown in Fig. 3. The results reveal that silt is the dominant size fraction throughout the sequence as the whole, ranging from 33.3% to 93.1%. The lower sequence in the 12.38-4.52 m interval, presents higher contents and a more stable composition of clays and silts than that of the upper sequence (4.52-1.60 m), which is marked by a saw tooth increase in sand content and by a low clay fraction however broadly correlated to the silt content.

The core base between 12.50 and 12.38 m depth (sub-unit 1a), is characterized by the predominance of sandy and coarse silty fractions. The following section between 12.38-4.52 m (sub-unit 1b), presents a broadly stable grain size distribution with 49.8% of fine silt, 31.5% of coarse silt, 12.5% of clay and 6.2% of sand. Nevertheless, at the top of this section (6.00-4.52 m), the clayish fraction increases while coarse silt decreases. The whole sequence exhibits low and unvaried values of mode, median and mean.

Between 4.52 and 1.60 m, grain size displays sharp changes, quite well correlated with the identified lithological unit 2 and as a whole, with increasing coarse silt and sandy fractions when compared with the lower unit 1. The clayish fraction is low and follows the fine silt pattern that reaches its highest content in sub-unit 2d and relative high content in sub-unit 2b. The most important variations are pointed out by the sandy and fine silty fractions varying between 4.52 and 4.02 m and between 3.85 and 3.73 m in levels 2a and 2c, respectively. These two grain sizes, as well as mode and median highlight the bi-modal sub-unit 2e with increased sandy fraction in its lower part and increased fine silts in its upper part. In combination with mode, the most frequently-occurring particle diameter, as well as median, corresponding to the 50 percentile on a cumulative curve, the mode/median ratio could indicate the predominate particles as fine, coarse, or equal contents of both. As presented in Fig. 3, the mode/median ratio at 12.38-4.52 m and 3.73-2.87 m intervals is less than 1, reflecting the dominant fine fraction while other depths are characterized by coarse fraction.

Finally, the different proportions of clay, silt and sand in lake sediments and in the catchment area, reflect the sorting of the detrital material during the river transport and depositional conditions.

Mineralogy

In combination with Fig. 4 and Fig. 5, XRD analyses on samples from the composite core indicate the present of (i) silicates dominated by quartz, feldspars (orthoclase, albite), mica (muscovite) and clay minerals (chlorite, illite, kaolinite, smectite and some palygorskite), all identified in the whole set of samples, and in some specific levels, minerals from amphibole and pyroxene groups as well as iron oxides (magnetite) that are of detrital origin; (ii) carbonates that can be detrital, biomediated or chemically precipitated whether in evaporitic environments or not; (iii) evaporitic minerals as halite and gypsum, and (iv) other minerals such as iron sulfides (greigite and pyrite) that are of early diagenetic origin.

The presence of evaporitic minerals, such as halite and gypsum in almost all the samples, points out relatively saline to highly saline conditions in the lake during all concerned period (Fig. 4d).

Quartz, feldspars and mica

Quartz, as well as feldspars and mica display the same pattern with increased contents at the core bottom (sub-unit 1a), and in three above sections of the unit 2 (sub-units 2a, c and e), with 38%, 27% and 28% of the total sediment respectively (Fig. 4). The lowest contents of these minerals, even less than 1%, are recorded in sub-unit 2d. According to the results obtained from the catchment area, the geological formation 6 and possibly some others (formations 2, 7) represent important sources for these three minerals. When these minerals are in lower contents, their origin cannot be clearly identified, but one can observe that the lowest contents of this mineralogical assemblage as in the sub-unit 2d, are in the geological formations 4, 5 and 8.

Clay minerals

Among all clay minerals in the clay-sized siliceous fraction, illite and smectite dominate the lake sedimentation (Fig. 5), less abundant chlorite fluctuates similarly to illite, kaolinite shows lowest percentages. Sediments from unit 1 (12.50-4.52 m), are characterized by relatively stable proportions of different clay minerals with the predominance of smectite (51.9%), followed by illite (33.2%), chlorite (11%) and kaolinite (4.3%). The upper unit 2 demonstrates more contrasted clay minerals pattern.

Sediments in the 4.52-3.73 m interval that correspond to sub-units 2a, 2b and 2c, exhibit (i) increasing proportions of illite (up to 62.0%) and chlorite, (ii) decreasing contents of smectite (until 10.3%), and (iii) low and stable proportions of kaolinite. In sediments comprised between 3.73 and 2.87 m, i.e. sub-unit 2d, both smectite and illite present relatively stable and equal proportions of 40%. The two last units 2e and 2f units exhibit broadly the same pattern with relatively low, changing contents of smectite (13.7%) and high, fluctuating contents of illite (61.3%). Chlorite reaches its highest values of 26.2% in sub-unit 2e before decreasing while kaolinite stays low overall the whole core and just increases up to 18.4% at the top sequence. The composition variations of different minerals throughout the whole composite core reflect quite a good agreement with different lithological formations from the catchment area. Indeed, high contents of smectite in the lake sediment are also recorded in the catchment area for geological formations represented by samples 1, 2, 4 and 7. Illite rich sediments that display increased contents of chlorite too, are present in samples 3 and 6, but also in 2, 5 and 8. Finally, the high contents of kaolinite in the upper part of the core are also recorded in samples 5 and 8. Smectite crystallinity index is around 0.8 in the lower part of the core (unit 1) and scales further above but still remaining below 1.5. Meanwhile illite crystallinity in the under lying unit 1, varying values between 0.2 and 0.5 that reflect very well-to well-crystallized illite, suggests some chemical transformations [START_REF] Ehrmann | Clay Minerals in Cenozoic Sediments Off Cape Roberts (Mcmurdo Sound, Antarctica) Reveal Palaeoclimatic History[END_REF]. As values obtained for samples from the catchment area (Fig. 5), they indicate well crystallized smectite and illite [START_REF] Ehrmann | Clay Minerals in Cenozoic Sediments Off Cape Roberts (Mcmurdo Sound, Antarctica) Reveal Palaeoclimatic History[END_REF]. In the upper sequence named as unit 2, illite crystallinity index remains stable and low, equaling to 0.1-0.2 that indicates very well crystallized illite, which is well correlated with samples in the catchment area. Illite chemistry index fluctuates around 0.2 all throughout the sediments. This parameter when lower than 0.4, reflects Fe and Mg-rich illite [START_REF] Diekmann | Clay Mineral Fluctuations in Late Quaternary Sediments of the Southeastern South Atlantic: Implications for Past Changes of Deep Water Advection[END_REF][START_REF] Ehrmann | Clay Minerals in Cenozoic Sediments Off Cape Roberts (Mcmurdo Sound, Antarctica) Reveal Palaeoclimatic History[END_REF]. The illite chemistry as well as illite and smectite crystallinities in the core sediments present values identical to those of the formations of the catchment area, thus suggesting the high stability and detrital origin of the clays, acting rather by erosion than chemical weathering.

Carbonates

Carbonate contents display values from ca 20 to 93% and their variations are correlated with defined lithological units (Fig. 4e). Unit 1 starts with low values of about 20% that increase at the beginning of subunit 2b up to 60% and remain relatively stable throughout the core. Above unit 1, carbonate contents clearly fluctuate: they decrease to 20-25% in sub-units 2a, 2c, 2e and increase in 2b, 2d and 2f reaching the highest values of 93% in sub-unit 2d. The carbonate curve evidences the same succession of environmental changes to that obtained by [START_REF] Tudryn | Late Quaternary Environmental Changes of Lake Urmia Basin (Nw Iran) Inferred from Sedimentological and Magnetic Records[END_REF], although due to different method used, either the calculations from XRD diagrams applied in the present study or the Mélières mono-calcimeter [START_REF] Tudryn | Late Quaternary Environmental Changes of Lake Urmia Basin (Nw Iran) Inferred from Sedimentological and Magnetic Records[END_REF], the values are different. The former might be slightly overestimated due to a fraction of non-crystalline material that may be present in the sample, while the latter allows calcium carbonate to be measured but not the most resistant dolomite.

Carbonate fraction consists of three minerals: calcite, aragonite and dolomite (Fig. 4). Aragonite is absent in sub-units 1a, 2a, 2c and 2e, whereas it is present elsewhere in the sediment either as mud or as major component of fecal pellets. Aragonite represents the major part of the carbonate fraction with percentages even as high as 92% where shrimp's fecal pellets are particularly abundant (sub-unit 2d, Fig. 2h) and its general pattern is similar to that of total carbonate. Calcite and dolomite evolve as a whole between 0 and 15%. In the very narrow sub-unit 2b calcite reaches the highest content of 38% and then contains low and stable content from sub-unit 2d to the core top, it displays inversed pattern to that of aragonite. Dolomite also displays such inversed pattern to aragonite all along the sequence with clear increases of percentages in sub-units 1a, 2a, 2c and 2e (Fig. 4).

The calcite crystallinity index presents values of about 0.10 along the core. A single level is characterized by the highest calcite crystallinity index of 0.26 shown in sub-unit 2b (Fig. 4). Since (i) the higher value the crystallinity index, the worse the carbonate is crystallized, and (ii) calcite crystallinity obtained for samples from the catchment area ranges between 0.08 and 0.12, it appears that most of the calcite in the core sediments present the same good crystallinity and is thus of detrital origin. According to [START_REF] Fontes | Stable Isotope and Radiocarbon Balances of Two Tibetan Lakes[END_REF][START_REF] Fontes | Holocene Environmental Changes in Lake Bangong Basin (Western Tibet). Part 1: Chronology and Stable Isotopes of Carbonates of a Holocene Lacustrine Core[END_REF], only the calcite found at depths from the sub-unit 2b can be considered as authigenic rapidly precipitated through biogenic activity or through direct chemical precipitation in lake water.

The crystallinity index of dolomite in lake sediments displays scattered values between 0.06 and 0.38 while it is evolving from 0.08 to 0.12 in samples from the catchment area. Following the example of calcite, wellcrystallized dolomite is thus of detrital origin (low index value; sub-units 1a, 2a, 2c and 2e), while its poor crystallinity is related to authigenic conditions of precipitation (high index value; sub-units 1b, 2b, 2d and 2f). The formation of dolomite requires drastic chemical conditions rarely found in lacustrine environments except when occurring as in situ replacement product of calcium carbonate sediments, particularly in evaporitic sites [START_REF] Pierre | Supratidal Evaporitic Dolomite at Ojo De Liebre Lagoon; Mineralogical and Isotopic Arguments for Primary Crystallization[END_REF]. However, dolomite precipitation is driven by both high alkalinities and low Ca 2+ /Mg 2+ and SO4 2-concentrations in the solution, the two latter resulting of massive calcium minerals precipitation (carbonates, sulfates) and/or a bacterial sulfate reduction [START_REF] Lippmann | Crystal Chemistry of Sedimentary Carbonate Minerals[END_REF]. In Lake Urmia composite core, the direct crystallization of dolomite from aqueous solutions could be considered in relation with highly evaporative phases (alkaline status of the lake) as observed in the Coorong area in Australia or in the Deep Spring Lake basin in California [START_REF] Alderman | Dolomite Sedimentation in the South-East of South Australia[END_REF][START_REF] Alderman | Occurrence of Hydromagnesite in Sediments in South Australia[END_REF][START_REF] Alderman | Occurrence of Magnesite-Dolomite Sediments in South Australia[END_REF][START_REF] Alderman | A Dolomite Reaction Series[END_REF][START_REF] Peterson | Radiocarbon Studies of Recent Dolomite from Deep Spring Lake[END_REF][START_REF] Skinner | Precipitation of Calcian Dolomites and Magnesian Calcites in the Southeast of South Australia[END_REF][START_REF] Von Der Borch | The Distribution and Preliminary Geochemistry of Modem Carbonate Sediments of the Coorong Area[END_REF][START_REF] Peterson | Growth of Dolomite Crystals[END_REF][START_REF] Clayton | Isotope Studies of Dolomite Formation under Sedimentary Conditions[END_REF][START_REF] Der Borch | Spherular Modern Dolomite from the Coorong Area[END_REF]. Moreover, dolomite precipitation occurs concomitantly with the formation of aragonite that (i) displays high crystallinity index (Fig. 4k), (ii) requires a high Mg 2+ content in waters to become the stable species of calcium carbonate and (iii) can be related to the chemical or biochemical precipitation, both reflecting evaporative conditions [START_REF] Müller | Formation and Diagenesis of Inorganic Ca-Mg Carbonates[END_REF][START_REF] Eugster | and geomorphology[END_REF][START_REF] Kelts | Holocene Sedimentology of Hypersaline Lake Urmia, Northwestern Iran. %J Palaeogeography[END_REF][START_REF] Fontes | Stable Isotope and Radiocarbon Balances of Two Tibetan Lakes[END_REF][START_REF] Fontes | Holocene Environmental Changes in Lake Bangong Basin (Western Tibet). Part 1: Chronology and Stable Isotopes of Carbonates of a Holocene Lacustrine Core[END_REF].

Chronology

The 14 C AMS dating performed both on organic fractions (diffused organic matter and hand-picked charcoal) and on inorganic and biomediated (i.e. fecal pellets) carbonates from cores Golman 6 and Golman 7 are presented in Table 2.

Considering all the data gathered on the carbonate fraction over the composite core and on the catchment as well as the modern hydrogeochemical lake system, we have to implement two age corrections: (i) the first one related to the detrital carbonate fraction in the dated samples, and (ii) the second one taking into account the hard-water effect of the modern lake surface water, considering that authigenic materials such as inorganic carbonates and organic matter are formed in the lake upper water layer.

(i) Correction 1 is applied on bulk samples when a detrital carbonate fraction is evidenced; the 14 C activity of the authigenic carbonates can be written as AM = X*AAC + ADC*(1-X) with AM, the measured 14 C activity on the total carbonate fraction; X, the percentage of authigenic carbonate in the bulk sample; AAC and ADC, the 14 C activities of the authigenic and detrital carbonates respectively. Assuming that detrital carbonate originating from the watershed is 14 C-free (ADC = 0), we can state AAC = AM /X as proposed by Fontes et al. [START_REF] Fontes | Stable Isotope and Radiocarbon Balances of Two Tibetan Lakes[END_REF][START_REF] Fontes | Holocene Environmental Changes in Lake Bangong Basin (Western Tibet). Part 1: Chronology and Stable Isotopes of Carbonates of a Holocene Lacustrine Core[END_REF]. This correction is applied on all the dated samples containing a detrital fraction, either calcite or calcite and dolomite through XRD half-width of the main peak for each mineral (Table 2): both of dolomite and calcite are considered as detrital (authigenic) when their crystallinity indexes are lower (higher) than 0.12 according to the crystallinity index of catchment samples.

(ii) Correlation 2 is applied on 14 C dates established from carbonate activities after correction 1 if a detrital fraction is present in the bulk sample; knowing that the 14 C activity of atmosphere CO2 was measured at 101.8 pMC in 2016 [START_REF] Hua | Atmospheric Radiocarbon for the Period[END_REF], the present-day 14 C activity of the lake water is 680 yr. The most common hypothesis is to consider that this reservoir effect in the past [START_REF] Fontes | Stable Isotope and Radiocarbon Balances of Two Tibetan Lakes[END_REF][START_REF] Fontes | Holocene Environmental Changes in Lake Bangong Basin (Western Tibet). Part 1: Chronology and Stable Isotopes of Carbonates of a Holocene Lacustrine Core[END_REF][START_REF] Gasse | Hydrological Changes in the African Tropics since the Last Glacial Maximum[END_REF]. However, when 14 C dates are plotted against depth, a consistent evolution appears with all carbonate and organic levels dated above 6 m depth (above 22 kry BP). With respect to the ages defined on charcoal which represent the equilibrium with atmospheric CO2, a different of 2000 years can be defined which can be applied to all the other ages.

From 12.5 to 4.52 m depth, the 14 C AMS chronology is based on 4 dating that are in agreement with the lithostratigraphy, with a sedimentary rate (msr) of 0.89 mm.yr-1 (Table 2). This msr is relatively high due to the presence of unrecovered muddy sections during coring, which artificially increase the sedimentation rate. From 4.52 m depth to the core top, two phases are recorded, i.e. 4.52-2.87 m and 2.87-1.6 m intervals, associated to msr of 0.12 and 0.40 mm.yr -1 respectively.

Discussion

The palaeoenvironmental history of Lake Urmia

Lake Urmia is a complex hydrological system governed by the climatic evolution in the eastern Mediterranean area and Western Asia, but also by local factors. Among local factors, the topography, geology and tectonics in the catchment area as well as the lake basin hydrology, which is driven by the net effect of precipitation, surface runoff, evaporation, and evapotranspiration processes [START_REF] Eugster | Behavior of Major Solutes During Closed-Basin Brine Evolution[END_REF], are of upmost significance during depositional processes in the lake. In its south western part of Lake Urmia concerned by this study, the contrasting topography and differences in altitude of more than 1500 m between the most distant sources of detrital material and the lake favor erosional processes independently of the climate and water availability. Magmatic, metamorphic and sedimentary rocks are present in the catchment and minerals from these rocks constitute an important part of the lake sediments.

Carbonates, feldspars and mica undergo chemical alteration relatively easily among all these minerals [START_REF] Chamley | Clay Mineralogy[END_REF]. These detrital minerals are dramatically poor in two sub-units of the unit 2 (2b: 4.02-3.85 m; 2d: 3.73-2.87 m), while elsewhere they represent a major part of the sediments and highlight rather erosional processes in the catchment area than chemical ones. Additionally, the authigenic carbonate integrating the aragonite fraction either chemically or biological mediation precipitated, represents a significant part of the lake sediments. Halite and gypsum indicate the evaporitic conditions in the lake basin as a whole. Iron sulfides identified in several parts of the sediment highlight the early diagenesis in the sediment in anoxic, sulfate-reducing environment [START_REF] Tudryn | Late Quaternary Environmental Changes of Lake Urmia Basin (Nw Iran) Inferred from Sedimentological and Magnetic Records[END_REF]. Despite the complexity of 14 C signatures of authigenic carbonate and from organic matter samples (either terrestrial or lacustrine) we established a reliable chronology of the lake evolution for the last 30 kyr. As the age scale of composite core is presented in Fig. 6, the data reflect the lake history both general climate trends and fundamental changes in local hydrology through well-defined intervals.

The lake at ca 30 cal kyr BP

The interval starts with light brown sandy sediments and is followed by coarse silt of blackish to dark grey color due to abundant vegetation remains. This sequence is characterized by high contents of detrital silicates, including both predominant coarse particles (such as quartz, feldspars and mica) and few fine particles (Fig. 6). In addition, a low abundance of aragonite-free carbonates is recorded with the presence of calcite and dolomite, both from detrital origin. Such a sedimentary composition dominated by coarse grain sizes indicates the direct influence of the Shahr Chay River at the coring site and erosional processes in the catchment rather than chemical weathering that implies water availability. Silicates originating principally from phyllite and sandstone, are present in the upper part of the catchment area (geological formation sample 6 in Table 3), while calcite and dolomite derive from carbonate rich formations 3 and 8.

According to [START_REF] Tudryn | Late Quaternary Environmental Changes of Lake Urmia Basin (Nw Iran) Inferred from Sedimentological and Magnetic Records[END_REF], the light brown sand at the beginning of the interval and the presence of detrital magnetite highlight well oxygenated conditions during the sedimentation at the coring site.

Moreover, pressurized gas and brine are captured in this sand with less water salinity than in today's lake waters. Above the sandy level, blackish and dark grey silts are rich in plant remains identified as C3 plants with δ 13 C around -25‰ PDB (Table 2) and in greigite, an authigenic iron sulfide that indicates the anoxic and sulfate-reducing conditions within the sediment [START_REF] Curtis | Mineralogical Consequences of Organic Matter Degradation in Sediments: Inorganic/Organic Diagenesis[END_REF]. Greigite being magnetic mineral, its presence is highlighted by high magnetic susceptibility on Fig. 6a. As noted by [START_REF] Tudryn | Late Quaternary Environmental Changes of Lake Urmia Basin (Nw Iran) Inferred from Sedimentological and Magnetic Records[END_REF], the high organic content here may reflect an increased input of organic detritus from the river, although the decreasing grain size of the sediment and its poor oxygenation more likely suggest the development of a saltmarsh with high biological productivity rather than a higher riverine activity. Such a start of the sedimentary sequence reflects erosional processes in the catchment and a low lake level, without lacustrine or very shallow conditions in the coring area, reflecting rather dry conditions and a low water availability on the catchment area.

The 29.85-20.21 cal kyr BP interval

The grey, homogeneous sedimentation is dominated by fine silts and clays, with some interbedded millimetric levels of coarse silt and sand. Detrital silicates (mainly quartz, mica and feldspars) represent about 30% of the sediment. In the clay fraction, well-crystallized smectite dominates reaching the highest contents of the whole sequence (12% in total sediment). The ratio smectite versus illite stays close to 2, indicating broadly invariable proportions of these minerals all along the interval (Fig. 6). This is compatible with the erosion of the geological formations 7 and 1, as well as 4 and 2, that bring abundant smectite from the catchment area enough to explain the high smectite contents. However, chemical ongoing weathering or precipitation in the lake salty environment [START_REF] Chamley | Clay Mineralogy[END_REF]) cannot be totally excluded since (i) halite is present here (but also all along the core), and (ii) smectite related to the chemical weathering especially in the formations 7 and 1, would indicate enough water in the catchment for such process. In addition, carbonates account for 62% in the suite of minerals with 38% of aragonite, 16% of calcite, and 8% of dolomite, in which aragonite is of authigenic origin and calcite is of detrital one, while dolomite has both authigenic and detrital origins according to their respective crystallinity indexes.

Such detrital fraction in the core sediment suggests that the environment is still dominated by physical weathering and erosion on the catchment area, with nevertheless, low transport energy conditions, reflecting lacustrine conditions established in the coring site. At the beginning of the interval, aragonite that was absent before at the core base appears and increases rapidly from 25 to 50% of the sediment, while authigenic dolomite occurs in several parts of the interval, both constituting the carbonaceous mud. The formation of both aragonite and dolomite requires a high Mg 2+ content in waters to become the stable species of calcium and magnesium carbonates, and thus reflect evaporative lacustrine conditions [START_REF] Alderman | Dolomite Sedimentation in the South-East of South Australia[END_REF][START_REF] Alderman | Occurrence of Hydromagnesite in Sediments in South Australia[END_REF][START_REF] Alderman | Occurrence of Magnesite-Dolomite Sediments in South Australia[END_REF][START_REF] Alderman | A Dolomite Reaction Series[END_REF][START_REF] Peterson | Radiocarbon Studies of Recent Dolomite from Deep Spring Lake[END_REF][START_REF] Skinner | Precipitation of Calcian Dolomites and Magnesian Calcites in the Southeast of South Australia[END_REF][START_REF] Peterson | Growth of Dolomite Crystals[END_REF][START_REF] Clayton | Isotope Studies of Dolomite Formation under Sedimentary Conditions[END_REF][START_REF] Müller | Formation and Diagenesis of Inorganic Ca-Mg Carbonates[END_REF][START_REF] Eugster | and geomorphology[END_REF][START_REF] Kelts | Holocene Sedimentology of Hypersaline Lake Urmia, Northwestern Iran. %J Palaeogeography[END_REF], as do halite and gypsum. The intensity of evaporative conditions probably experienced several fluctuations that can be deduced from the decrease of evaporate minerals and the simultaneously decrease of authigenic dolomite between 26.50 and 24.30 kyr BP, and at ca 22.90 kyr BP (Fig. 6g andi).

Detrital and authigenic fractions of the sediment show a clearly lacustrine environment established at the coring site during this interval. Meanwhile, the quite small grain size suggests low transport energy conditions in phase with a relatively high water level. The water salinity fluctuation is highlighted by simultaneous changes in the authigenic dolomite contents and evaporites. The interval is characterized by relatively wet although cold conditions that favor erosional processes in the catchment area even if chemical weathering was probably acting too.

In addition, according to previous studies [START_REF] Wurtsbaugh | Limnological Control of Brine Shrimp Population Dynamics and Cyst Production in the Great Salt Lake, Utah[END_REF]Abbaspour and Nazaridoust, 2007;Agh et al., 2008;[START_REF] Esmaeili Dahesht | The Fluctuations of Physicochemical Factors and Phytoplankton Populations of Urmia Lake[END_REF], the absence of fecal pellets could be attributed to (i) very low lake level and thus too highly saline conditions for shrimps development (more than 300 g.L -1 ), or (ii) a very high water level with too low salinity (below 100 g.L -1 ) implying the presence of predators that do not allow the shrimps development, or (iii) very cold lake water that also do not allow the shrimps development (ca 3 °C). However, this sequence (apart two thin levels) could reflect a very high water level with cold temperature.

Finally, [START_REF] Tudryn | Late Quaternary Environmental Changes of Lake Urmia Basin (Nw Iran) Inferred from Sedimentological and Magnetic Records[END_REF] showed that magnetic minerals point out early diagenetic processes in anoxic sediment and possibly a bad ventilation of the bottom water, in good agreement with a high lake level.

Additionally, the decrease of illite crystallinity within this time interval could also be related to the specific post-deposition environment in the lake sediments. The data thus indicate that after a low lake stand at ~30 cal kyr BP, the lake level increased and, nevertheless some fluctuations, remained high until 20.21 cal kyr BP.

The 20.21-15.33 cal kyr BP phase

Sediments of the 20.21-15.33 kyr BP interval consist in (i) brown sands and silts with high contents of silicates as quartz, mica and feldspars, quick and short time illite and chlorite peaks, decrease of smectite and (ii) low carbonate contents with no aragonite, some calcite and more dolomite, both of detrital origin as indicated by their low crystallinities. These parameters thus indicate detrital input into the core site associated to physical weathering with erosion from geological formation 6 and dolomite-rich formations 3 and/or 8, and with no authigenic minerals. It is suggested that sediments during this period were deposited in relatively dry conditions, a low lake level and a well-oxygenated environment.

5. This following sequence is characterized by increasing clays and fine silt, in which silicates as quartz, mica and feldspars, only account for 20% (Fig. 6). With 66.2% of total sediment, the carbonate mud is made of aragonite (31.6%), calcite (23.5%) and dolomite (11.1%). According to the crystallinity index values, both dolomite and calcite are entirely of authigenic origin. Meanwhile these parameters clearly indicate lacustrine conditions as the same with 29.85-20.21 cal kyr BP interval. In contrast, the presence of the authigenic calcite between 15.33 and 13.27 cal kyr BP suggests less evaporative conditions than before, without authigenic calcite [START_REF] Müller | Formation and Diagenesis of Inorganic Ca-Mg Carbonates[END_REF]. Even if slightly advanced, two thousand years lasting in this interval shows timing in good agreement with the Bölling/Alleröd warming within Post-Glacial period as observed through Greenland ice cores (Fig. 6j).

The 13.27-11.82 cal kyr BP interval

The environmental conditions are similar to those recorded between 20.21 and 15.33 cal kyr BP. Indeed, sediments are marked by an increase in grain sizes and detrital silicates input, the dominance of illite and chlorite in the clayish fraction and the decrease in carbonate contents. Within carbonate fraction, aragonite is absent while few calcite and abundant dolomite of detrital inputs are present. All these parameters as well as the presence of magnetite indicate a well-oxygenated and close to the river mouth environment at the coring site, indicating a very low lake level. This regressive stage of the lake corresponds to the Younger Dryas cooling before the Holocene (Fig. 6j).

The 11.82-5.64 cal kyr BP interval

The sequence is characterized by fine-grained sediments, with very low contents of detrital minerals and the predominance of an authigenic carbonate fraction, indicating clearly the re-establishment of open lacustrine conditions. The detrital fraction of this section has higher clay mineral contents than the underlying section, and contains equal proportions of smectite and illite, with some added detrital calcite.

In the carbonate fraction, authigenic dolomite and huge contents of aragonite are present in the calcareous mud, mainly under the form of aragonite shrimp fecal pellets that are the dominant component of the sediment (Fig. 2 and7). The presence of these minerals indicates a lacustrine environment with high water salinity as like the period recorded at 29.85-20.21 cal kyr BP during which nevertheless, the presence of the shrimps Artemia is not recorded. According to previous studies, the abundance of Artemia fecal pellets is related to the water salinity between 100 and 300 g.L -1 and other parameters including temperature, that make favorable conditions for shrimps development [START_REF] Wurtsbaugh | Limnological Control of Brine Shrimp Population Dynamics and Cyst Production in the Great Salt Lake, Utah[END_REF]Agh et al., 2008;[START_REF] Esmaeili Dahesht | The Fluctuations of Physicochemical Factors and Phytoplankton Populations of Urmia Lake[END_REF][START_REF] Sharifi | The Vanishing of Urmia Lake: A Geolimnological Perspective on the Hydrological Imbalance of the World's Second Largest Hypersaline Lake[END_REF]. In several levels, dark and white pellets are mixed, the dark ones being older and reworked according to Kelts and Sharabi (1986). The presence of some iron sulfides, suggests a bad ventilation of the bottom water [START_REF] Tudryn | Late Quaternary Environmental Changes of Lake Urmia Basin (Nw Iran) Inferred from Sedimentological and Magnetic Records[END_REF]. The end of this section is marked by sharp changes in the lithology and all parameters (Fig. 2c and7).

The 5.64-4.10 cal kyr BP spell

This interval is divided into two parts. The lower part is characterized by coarse, sandy black sediment with abundant organic remains and authigenic iron sulfide, i.e. greigite. The 14 C dating performed on charcoal at 2.80 m depth gives an age of 5.48 cal kyr BP, in good agreement with the 4.94 cal kyr BP age also obtained on charcoal and collected from the neighboring core Golman 5 at 2.66 m depth indicated by [START_REF] Tudryn | Late Quaternary Environmental Changes of Lake Urmia Basin (Nw Iran) Inferred from Sedimentological and Magnetic Records[END_REF]. In the upper part of this sequence, silty and detrital minerals prevail, mainly with quartz, feldspar, mica, illite, and few carbonate-calcite and dolomite being of detrital origin too. This suggests the drying out or very shallow conditions at the coring site similarly to what is recorded at the beginning of the sequence i.e. at ~30 cal kyr BP. Nevertheless, contrary to the core bottom, the dated charcoal samples exhibit distinct δ 13 C values of -26.5, -25.5 ‰ and of -13.5, -14.5 ‰ vs PDB (Table 2), characterizing C3 and C4 plants respectively and emphasizing that both coexist on the watershed at the time of deposition. The C4 vegetation episode seems to have lasted at least 600 years, between 5.64 and 4.10 cal kyr BP, and likely indicates a warmer and drier episode than the one occurring at 30 cal kyr

cal kyr BP interval

Abundant shrimp fecal pellets are found in this last sequence, reflecting the lake level rise and thus a recover of open lacustrine environment at the coring site. The predominant sandy fraction made of detrital silicates reflects a high energy transport from the nearest inflow, Shahr Chay River. Furthermore, the high carbonate content gathers authigenic aragonite and dolomite as well as some detrital calcite. Authigenic carbonates and shrimp fecal pellets indicate a high evaporation rate, with a water salinity comprised between 100 and 300 g.L -1 , and temperature high enough to allow the shrimp development [START_REF] Sharifi | The Vanishing of Urmia Lake: A Geolimnological Perspective on the Hydrological Imbalance of the World's Second Largest Hypersaline Lake[END_REF].

Lake Urmia history at a regional scale

The results obtained here show the importance of detrital input related to the physical weathering in the catchment area and indicate several Lake Urmia low and high stands. The intense erosional processes have also been described by Mirzapour et al. (2021a;2021b). The lake water level changes clearly mark the alternation of relatively dry and wetter periods in the lake catchment, but still with high evaporation conditions and saline lake waters even in the wettest periods.

After the low stand at ~30 cal kyr BP, the lake level increased and remained high until the Last Glacial Maximum at ca 20 cal kyr BP at the coring site. Our results confirm those obtained by Djamali et al. (2008a) who proposed a high water level during the last glacial period, on the opposite to [START_REF] Stevens | Hydroclimatic Variations over the Last Two Glacial/Interglacial Cycles at Lake Urmia, Iran[END_REF] that indicated no perennial lake and clearly arid climate at Lake Urmia. Moreover, our results are in good agreement with evolution of surrounding lakes at a regional scale such as the high stands reported from Lake Zeribar [START_REF] Wasylikowa | Palaeolimnology of Lake Zeribar, Iran, and Its Climatic Implications[END_REF] and Lake Van (Kuzucuoğlu et al., 2010) as well as from the Black Sea [START_REF] Shumilovskikh | Orbital-and Millennial-Scale Environmental Changes between 64 and 20 Ka Bp Recorded in Black Sea Sediments[END_REF].

From 20.21 to 2.34 cal kyr BP, the lake experienced water level fluctuations with three relatively high stands (i) between 15.33-13.27 cal kyr BP during the warming Bolling/Alleröd event, (ii) from 11.82 to 5.64 cal kyr BP, during the Early and Mid-Holocene and (iii) during the 4.10-2.34 cal kyr BP, Late Holocene interval registered in our cores. These intervals were separated by low lake stands with completely dried-out or close to the lake water line conditions at a coring site (i) after the Last Glacial Maximum between 20.21 and 15.33 cal kyr BP, (ii) during the Younger Dryas from 13.27 to 11.82 cal kyr BP, and (iii) at the transition from Mid to Late Holocene, during the 5.64-4.10 cal kyr BP interval (Fig. 6).

Previous studies by [START_REF] Kelts | Holocene Sedimentology of Hypersaline Lake Urmia, Northwestern Iran. %J Palaeogeography[END_REF] on Lake Urmia identified 3 relatively high lacustrine stands and 2 low ones for the Late Pleistocene and Holocene, and proposed ca 9-7.5 kyr BP for the lacustrine period that certainly corresponds to that between 11.82-5.64 cal kyr BP in our record; indeed, authors highlighted the lack of readily dateable material in their study. [START_REF] Stevens | Hydroclimatic Variations over the Last Two Glacial/Interglacial Cycles at Lake Urmia, Iran[END_REF] indicated dry conditions with the short-term lacustrine episode at ~14 kyr, drying out probably marking the Younger Dryas and no re-establishment of lacustrine conditions until ca 10 kyr. Holocene reconstructions by [START_REF] Sharifi | The Vanishing of Urmia Lake: A Geolimnological Perspective on the Hydrological Imbalance of the World's Second Largest Hypersaline Lake[END_REF] suggested wet early Holocene and frequent dry episodes during Mid-Late Holocene.

The lacustrine records from Zagros Mountains (lakes Zeribar, Mirabad, Dasht-e Arjan) indicate dry conditions and low lake levels during the early Holocene [START_REF] Stevens | Timing of Atmospheric Precipitation in the Zagros Mountains Inferred from a Multi-Proxy Record from Lake Mirabad[END_REF][START_REF] Wasylikowa | Palaeolimnology of Lake Zeribar, Iran, and Its Climatic Implications[END_REF][START_REF] Aubert | A Major Hydrobiological Change in Dasht-E Arjan Wetland (Southwestern Iran) During the Late Glacial-Early Holocene Transition Revealed by Subfossil Chironomids[END_REF], while clearly lacustrine conditions dominated in Lake Urmia during this time. Quite wet conditions at the beginning of the Holocene, and changing ones during the Late Holocene, are also indicated from Lake's Neor basin area located in the NW Iran [START_REF] Sharifi | Abrupt Climate Variability since the Last Deglaciation Based on a High-Resolution, Multi-Proxy Peat Record from Nw Iran: The Hand That Rocked the Cradle of Civilization[END_REF][START_REF] Aubert | Late Glacial and Early Holocene Hydroclimate Variability in Northwest Iran (Talesh Mountains) Inferred from Chironomid and Pollen Analysis[END_REF], and from Anatolian lakes (e.g. Van, Gölhisar, Eski Acigöl). According to many authors, Anatolian lakes were subject to evaporation during the Mid-to-Late Holocene, when water levels fell and even led to the lake drying out [START_REF] Landmann | Dating Late Glacial Abrupt Climate Changes in the 14,570 Yr Long Continuous Varve Record of Lake Van[END_REF][START_REF] Roberts | The Tempo of Holocene Climatic Change in the Eastern Mediterranean Region: New High-Resolution Crater-Lake Sediment Data from Central Turkey[END_REF][START_REF] Eastwood | Holocene Climate Change in the Eastern Mediterranean Region: A Comparison of Stable Isotope and Pollen Data from Lake Gölhisar[END_REF][START_REF] Jones | Quantifying Climatic Change through the Last Glacial-Interglacial Transition Based on Lake Isotope Palaeohydrology from Central Turkey[END_REF][START_REF] Jones | Interpreting Lake Isotope Records of Holocene Environmental Change in the Eastern Mediterranean[END_REF][START_REF] Roberts | Stable Isotope Records of Late Quaternary Climate and Hydrology from Mediterranean Lakes: The Isomed Synthesis[END_REF].

In Lake Urmia, transition from Mid to Late Holocene was marked by dry conditions and a low water level between 5.64 and 4.10 cal kyr BP. Such a dry event was identified during broadly the same time in Zagros Mountains [START_REF] Stevens | Timing of Atmospheric Precipitation in the Zagros Mountains Inferred from a Multi-Proxy Record from Lake Mirabad[END_REF] and in Anatolia [START_REF] Fontugne | From Pleniglacial to Holocene: A 14c Chronostratigraphy of Environmental Changes in the Konya Plain[END_REF]. This phase is likely linked to the drought event recorded at 5.2 cal kyr BP that was evidenced in the Soreq speleothem record [START_REF] Bar-Matthews | Late Quaternary Paleoclimate in the Eastern Mediterranean Region from Stable Isotope Analysis of Speleothems at Soreq Cave[END_REF] and in many others sites [START_REF] Staubwasser | Holocene Climate and Cultural Evolution in Late Prehistoric-Early Historic West Asia[END_REF]. The relatively wet early Holocene deduced from Lake Urmia is in contrast with the long delay in postglacial forest expansion at the beginning of the Holocene in the Southwest Asia that was pointed out by many authors [START_REF] Jones | Interpreting Lake Isotope Records of Holocene Environmental Change in the Eastern Mediterranean[END_REF][START_REF] Djamali | A 200,000-Year Record of the Brine Shrimp Artemia (Crustacea: Anostraca) Remains in Lake Urmia[END_REF][START_REF] Aubert | A Major Hydrobiological Change in Dasht-E Arjan Wetland (Southwestern Iran) During the Late Glacial-Early Holocene Transition Revealed by Subfossil Chironomids[END_REF].

Conclusion

In this paper, we conducted systematic investigations on grain size and mineralogy of detrital and authigenic compounds that includes detailed analyses of carbonate and clays assemblages on the sedimentary sequence retrieved from the southwestern part of Lake Urmia. Our results show important changes in the lake water level for the past ~30 kyr, likely attributed to the available humidity. Although further interpretation of the hydrogeochemical characteristics and mixing processing in the lake basin is needed, the consistency of the AMS 14 C chronology between 22 and 2 cal kyr BP enabled us to estimate a reservoir effect for the past, which is particularly rare for such salt lakes. This reservoir age of about 2000 years has made possible to define a reliable chronology in agreement with the lithostratigraphy but also matching with the major regional environment phases.

Our work benefitted from highly reliable, precise multi-proxy data. The palaeoenvironmental reconstruction suggests a humid Late Pleistocene before the Last Glacial Maximum, followed by frequent drier/wetter episodes from that time until today, including the humid early Holocene period and evaporative conditions during the Mid to Late Holocene transition. Being today on the eastern limit of the Mediterranean zone, NW Iran links Southern Europe, North Africa and Asia, and thus could be submitted to the respective influences of the air masses from the North Atlantic, the Indian monsoon, the Ponto-Caspian region and the Siberian anticyclone. Our results suggest that an atmospheric teleconnection existed between North Atlantic and the Western Iran during the last 30 kyr BP and will be of high interest for global understanding of climatic change in the past. Lake surface water E2476 93,46 0,250 540 20 -1,10 ----------------------------------------------------------------------------------------------------------------------------------------------Golman-5 core G5 2,34 Charcoal B2087 0,5824 0,20 4 343 25 -14,50 G5 2,66 Charcoal B2088 0,5787 0,20 4 394 22 -25,50

----------------------------------------------------------------------------------------------------------------------------------------------------------------Composite core (Golman-6 and Golman-7 cores) -------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------Composite core (Golman-6 and Golman-7 cores) (a) CaCO3: total carbonate fraction; OM: diffused organic matter; FP: fecal pellets (Artemia) (b) Error bars represent one sigma deviation (c) Accuracies on 13 C measurements are of ±0.05 and ±0.02% PDB for carbonates and organic matter, respectively (d) Stuiver, M., Reimer, P.J., and Reimer, R.W., 2021, CALIB 8.2 [WWW program] at http://calib.org

  Abbaspour, M. and Nazaridoust, A.J.I.J.o.E.S., 2007. Determination of Environmental Water Requirements of Lake

Figure captions Fig. 1

 captions1 Figure captions

Fig. 2

 2 Fig. 2 Down-core variation of simplified lithofacies from Lake Urmia sediments: (a) core Golman 6; (b)

Fig. 3

 3 Fig. 3 Down-core variation in lithology and in grain size distribution of Lake Urmia sediments and of

Fig. 4

 4 Fig.4Down-core variation in lithology and in total mineralogy of Lake Urmia sediments and of catchment

Fig. 5

 5 Fig. 5 Down-core variation in lithology and in clay mineral composition of Lake Urmia sediments and of

Fig. 6

 6 Fig. 6 Evolution of sedimentological parameters against a 14 C time scale: (a) magnetic susceptibility (susc.),

  Figure 3

Table captions Table 1

 captions1 Location and description of Lake Urmia cored sequences and of geological samples from the Shahr Chay River catchment. Numbering of cores and samples in the text and figures refers to this table.

Table 2

 2 AMS-14 C calibrated ages of Lake Urmia sediments. Sample depth refers to the composite core (see text). All corrections and calibration are detailed in paragraph " 14 C chronology".

Table 3

 3 Mineralogy including crystallinity of selected minerals, and grain-size parameters on the geological samples collected from the Shahr Chay River catchment.

Table 1

 1

						Altitude
		Site name	Comment on sampling	Latitude N	Longitude E	m asl
						±1 m
	Coring well	Golman 6	8 m deep	37°35′28.854″	45°16′33.834″	1270
		Golman 7	12.5 m deep	37°35′28.746″	45°16′33.75″	1270
		1	Pyroclastic and claystone with vertebrate fauna remains, andesitic to basaltic volcanics	37°34'48"	45°12'00"	1370
		2	High level piedmont fan and valley terraces deposits	37°32'24"	45°07'12"	1311
		3	Red Beds composed of red conglomerate, sandstone, marl, gypsiferous marl (mostly limestones)	37°28'48"	44°57'36"	1484
	Catchment area	4	Red Beds composed of red conglomerate, sandstone, marl, gypsiferous marl (pure marl)	37°23'24"	44°55'12"	1720
	samples	5	Red Beds composed of red conglomerate, sandstone, marl, gypsiferous marl	37°24'36"	44°52'48"	1614
		6	Phyllite, slate and meta-sandstone (Hamadan Phyllites)	37°22'12"	44°48'00"	2820
		7	High level piedmont fan and valley terraces deposits	37°28'48"	44°47'24"	1788
		8	Dark gray medium-bedded to massive limestone (limestone)	37°27'00"	44°45'00"	2246

  Apparent Hard Water Effect (HWE) calculated with a 14 C activity of atmosphere of 100 pMC __________________________________________________________________________________ (*) Apparent Hard Water Effect (HWE) calculated with a 14 C activity of atmosphere of 100 pMC

	G7	1,70	CaCO3		0,5580	0,320	4 265	26	4 560	2 560	2 720	-205/+30
	G7	1,85	OM	B2295	0,5306	0,002	5 090	25	3 090	3 090	3 295	-75/+65
	G7-S2	2.80	Charcoal	B2097	0,5547	0,400	4 735	22	4 730	4 730	5 475	-145/+105
	G7-S2	3,07	CaCO3	CaCO3	0,3334	0,420	8 825	34	8 730	6 730	7 595	-80/+70
	G7-S2	3,09	Black FP (**) A21543	0,3880	0,0036	7 600	80	(secondary carbonate precipitation suspected)
	G7-S2	3,09	White FP (**) A21542	0,3666	0,0035	8 060	80	8 060	6 060	6 920	-180/+240
	G7-S2	3,09	CaCO3	CaCO3	0,3579	0,410	8 300	33	8 300	6 300	7 215	-55/+90
	G7-S3	3,65	CaCO3	CaCO3	0,2377	0,530	11 540	42	11 520	9 520	10 850	-245/+225
	G7-S3	4,05	OM	B2297	0,1529	0,100	15 090	66	15 090	13 090	15 695	-230/+235
	G6-S2	4,40	OM	B2304	0,1124	0,0011	17 560	76	17 560	15 560	18 845	-135/+135
	G6-S2	4,60	CaCO3	62001	0,0662	0,120	21 810	140	19 470	17 470	21 115	-385/+575
	G6-S4	6,45	OM	B2300	0,0689	0,0005	21 490	63	19 490	17 490	23 510	-260/+255
	G7 S6b	8,85	OM	B2099	0,0830	0,123	23 240	82	23 240	21 240	25 610	-555/+375
	G7-S8	12.46	Charcoal	B2301	0,0005	0,001	25 590	96	25 590	25 590	29 950	-290/+165
	__________________________________________________________________________________
	(*)


Microsymposium

Acta Cryst. (2021), A77, C49

Pepsi-SAXS/SANS -small-angle scattering-guided tools for integrative structural bioinformatics

Sergei Grudinin 1 , Anne Martel 2 , Sylvain Prevost 2 1 CNRS, Grenoble, France; 2 ILL, Grenoble, France sergei.grudinin@inria.fr I will present some recent developments of our Pepsi package for integrative modeling of macromolecules guided by small-angle scattering profiles. These include very fast tools for the all-atom computations of X-ray and neutron small-angle scattering profiles, called Pepsi-SAXS and Pepsi-SANS, respectively [1,2]. These tools implement algorithms specifically designed to handle two notable properties of large macromolecules and their complexes, such as for instance viral capsids, namely their high flexibility and high degree of symmetry. Flexibility of macromolecules is not spontaneous but linked with their structure and function. Computationally, it can be often approximated with just a few collective coordinates, which can be computed e.g. using the Normal Mode Analysis (NMA). NMA determines low-frequency motions at a very low computational cost and these are particularly interesting to the structural biology community because they give insight into protein function and dynamics. On our side, we have proposed a computationally efficient nonlinear NMA method that can be applied to largest complexes from the Protein Data Bank (PDB), and which also very well preserves local stereochemistry [3][START_REF] Grudinin | Predicting protein functional motions: an old recipe with a new twist[END_REF][START_REF] Laine | HOPMA: Boosting protein functional dynamics with colored contact maps[END_REF].

Flexibility of macromolecules is often linked with their structure and function. Computationally, it can be approximated with just a few collective coordinates computed using the Normal Mode Analysis (NMA). NMA determines low-frequency motions at a very low computational cost. This technique is particularly interesting for the structural biology community as it allows extrapolating biologically relevant motions starting from high-resolution structures. Recently, we have shown that it can be extended to model local deformations and to better preserve the stereochemistry of the protein. We have developed a computationally efficient nonlinear NMA method that can be applied to the largest complexes from the Protein Data Bank (PDB) [3][START_REF] Grudinin | Predicting protein functional motions: an old recipe with a new twist[END_REF][START_REF] Laine | HOPMA: Boosting protein functional dynamics with colored contact maps[END_REF].

Large symmetrical protein structures have seemingly evolved in many organisms because they carry specific morphological and functional advantages compared to small individual protein molecules. Recently we have proposed a novel free-docking method for protein complexes with arbitrary point-group symmetry [6]. It assembles complexes with cyclic symmetry, dihedral symmetry, and also those of high order (tetrahedral, octahedral, and icosahedral). We also proposed an efficient analytical solution to the inverse problem, that is the identification of symmetry group with the corresponding axes and their continuous symmetry measures in a protein assembly [7][8].

With Pepsi-SAXS and Pepsi-SANS, one can leverage the above-mentioned developments, by optimizing structures along lowfrequency « normal modes », performing automatic and adaptive coarse-graining of molecular models, rescoring free-docking predictions, including those of symmetric assemblies, and also optimizing structural transitions. Structural models produced by Pepsi-SAXS/SANS were ranked top in the recent data-assisted protein structure prediction sub-challenge in CASP13 [START_REF] Hura | Small angle X-ray scattering-assisted protein structure prediction in CASP13 and emergence of solution structure differences[END_REF].