Marc Jolivet
email: marc.jolivet@univ-rennes1.fr

Philippe Boulvais

carbon isotope compositions of pedogenic carbonates since the cretaceous

Keywords: Global isotopic signal, Cretaceous-Quaternary, Pedogenic carbonates, Topography

niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

The oxygen and carbon isotope compositions of pedogenic carbonates represent archives of past climate and environmental changes [START_REF] Cerling | The stable isotopic composition of modern soil carbonate and its relationship to climate[END_REF][START_REF] Cerling | Carbon dioxide in the atmosphere: evidence from Cenozoic and Mesozoic paleosols[END_REF]Fox and Koch, 2004;Dworkin et al., 2005;[START_REF] Garzione | Rise of the Andes[END_REF]. The  18 O and  13 C values of pedogenic carbonates are controlled by a number of factors that can be grouped in two broad categories: local factors (evaporation, nature of the vegetation, soil respiration, soil depth, hydrology and elevation of the area, latitude, distance from the marine water source…) and global factors such as atmospheric CO2 pressure or atmospheric CO2 isotopic composition [START_REF] Jenny | The Soil Resource: Origin and Behavior[END_REF][START_REF] Allison | The effect of climate and vegetation on the oxygen-18 and deuterium profiles in soils[END_REF][START_REF] Cerling | Carbon dioxide in the atmosphere: evidence from Cenozoic and Mesozoic paleosols[END_REF][START_REF] Körner | Carbon isotope discrimination by plants follows latitudinal and altitudinal trends[END_REF][START_REF] Cerling | Stable carbon and oxygen isotopes in soil carbonates. Climate Change in Continental Isotopic Records[END_REF]. Based on this, paleosol stable isotope data are used to constrain the paleoenvironmental conditions for specific areas and periods of time.

More global climate signals are generally probed using the isotopic composition of marine carbonates or of marine and continental fossil records [START_REF] Zachos | Trends, rhythms, and aberrations in global climate 65 Ma to Present[END_REF][START_REF] Zeebe | Seawater pH and isotopic paleotemperatures of Cretaceous oceans[END_REF][START_REF] Pucéat | Thermal evolution of Cretaceous Tethyan marine waters inferred from oxygen isotope composition of fish tooth enamels[END_REF][START_REF] Amiot | Latitudinal temperature gradient during the Cretaceous Upper Campanian-Middle Maastrichtian: d 18 O record of continental vertebrates[END_REF]Yongdong Wang et al., 2014). These are used as input data in global-scale climate models in order to derive parameters such as atmospheric pCO2 values, oceanic water temperatures or wind patterns [START_REF] Licht | Asian monsoons in a late Eocene greenhouse world[END_REF][START_REF] Caves | Role of the westerlies in Central Asia climate over the Cenozoic[END_REF][START_REF] Ladant | Palaeogeographic regulation of glacial events during the Cretaceous supergreenhouse[END_REF]. Whereas long-term, global or at least very large scale trends in isotopic compositions of marine carbonate fossils or continental vertebrates have been described [START_REF] Pucéat | Thermal evolution of Cretaceous Tethyan marine waters inferred from oxygen isotope composition of fish tooth enamels[END_REF][START_REF] Amiot | Latitudinal temperature gradient during the Cretaceous Upper Campanian-Middle Maastrichtian: d 18 O record of continental vertebrates[END_REF], only a limited number of global analysis of pedogenic carbonates have been attempted to date (e.g. Ekart et al., 1999;[START_REF] Sheldon | Quantitative paleo-environmental and paleoclimatic reconstruction using paleosols[END_REF], despite these carbonates represent in-situ indicators of the climate conditions prevailing on-land.

J o u r n a l P r e -p r o o f

A growing dataset of oxygen and carbon isotope compositions is available from carbonate-bearing paleosols worldwide, unevenly covering a long period of time from the Paleozoic to the Quaternary. From this dataset we selected the isotopic values obtained from Cretaceous to Quaternary paleosols. Analyzing those data from a global perspective, over large periods of time, we show that the isotopic signal reflects local and global conditions at a given, relatively short period of time, and that long-term trends in the isotopic data also exist that can be correlated to biological, topographic or climatic conditions.

Data collection

In this study we use the data from 103 publications, corresponding to geological sites in both hemispheres covering large latitude ranges and distributed on the 5 continents (Fig. 1 and Supplementary Table S1). Only data that were provided as numbers in tables were selected, avoiding collecting data from graphs. In order to get a homogeneous dataset, we selected oxygen and carbon isotope compositions solely from samples that could be assigned with high confidence to pedogenic carbonates (nodules, rhizocretions and pedogenic calcretes), and for which the formation age and the present-day geographic position are indicated. Those samples for which diagenetic alteration has been demonstrated or suspected by the authors of the original publication have been rejected as well as those developed in sediment hosting inherited carbonate grains when this is indicated in the publication. In each individual study, when outliers exist but are not directly explained by factors such as diagenesis, inherited carbonate or potential analytical errors, they have been included in the dataset.

Soil CO2 is generally a two-components mixture between atmospheric CO2 and CO2 derived from in situ oxidation of organic carbon (referred as soil respiration). Both soil J o u r n a l P r e -p r o o f Journal Pre-proof pCO2 and  13 C values thus vary with depth from atmospheric values at the surface to a constant soil value at depth, leading to a spread in individual isotopic ratios. Except for very low soil respiration rates, both parameters should be constant below depths of about 50 cm [START_REF] Cerling | The stable isotopic composition of modern soil carbonate and its relationship to climate[END_REF][START_REF] Sheldon | Quantitative paleo-environmental and paleoclimatic reconstruction using paleosols[END_REF]. For studies dealing with Quaternary paleosols and indicating the sampling depth, the values from samples collected above a depth of 50 cm have not been selected. The sampling depth for older paleosols is generally not constrained and all values have been considered. A total number of 12167 data have been isolated. [START_REF] Sheldon | Using carbon isotope equilibrium to screen pedogenic carbonate oxygen isotopes: Implications for paleoaltimetry and paleotectonic studies[END_REF] recently proposed to use the difference between the carbon isotope composition of soil carbonate and that of soil organic matter  13 C =  13 Ccarb - 13 Corg to screen corresponding oxygen isotope values and reject those that do not correspond to soils in oxygen isotope equilibrium. However, most of the studies we used in this compilation do not include  13 Corg values. To preserve the homogeneity of our dataset we were thus unable to use this approach and did not screen the oxygen isotope values even when  13 Corg was available.

The  13 C values are given relative to the Pee Dee Belemnite (PDB or VPDB for the equivalent Vienna standard). All  18 O values are given relative to the Vienna Standard Mean Ocean Water (VSMOW) and data initially provided using VPDB scale were converted using  18 OVSMOW = 1.03091 ×  18 OVPDB + 30.91 [START_REF] Coplen | Comparison of stable isotope reference samples[END_REF] In order to investigate the existence of trends in the data over large time-scales, data have been compiled in five age groups using the ages indicated in the original papers (Fig. 2): Lower Cretaceous, Upper Cretaceous, Paleogene, Neogene and Quaternary. The paleo-location of the samples is reported on the paleogeographic maps of the PALEOMAP project (Scotese, 2014a, b, c, d) (Fig. 1). When not provided in the original J o u r n a l P r e -p r o o f publication, the original paleolatitude of the samples has been estimated using these maps or paleotectonic maps of the Tethyan region [START_REF] Dercourt | Atlas Peri-Téthys and explaining notes (Coord. S. Crasquin)[END_REF][START_REF] Barrier | Paleotectonic Reconstruction of the Central Tethyan Realm. Tectonono-Sedimentary-Palinspastic maps from Late Permian to Pliocene[END_REF].

Trends in  18 O values through time are also compared to the evolution of global hypsometry notably to assess the role of orographic barriers. The Cretaceous topography was obtained from the 2.8° latitude × 2.8° longitude paleogeographic reconstructions of [START_REF] Sewall | Climate model boundary conditions for four Cretaceous time slices[END_REF], based on the 1°× 1° paleo Digital Elevation Model (DEM) of the PALEOMAP project (http://www.scotese.com/Default.htm, [START_REF] Scotese | PALEOMAP Paleogeographic Atlas[END_REF]) modified using data from the literature and from the Deep Time Maps project of R. Blakey (https://deeptimemaps.com). The early Eocene paleo DEM is from [START_REF] Herold | A suite of early Eocene (~55 Ma) climate model boundary conditions[END_REF] and has a 2° × 2° grid resolution. The middle Miocene paleo DEM was taken from Frigola et al. (2018). This model is based on a previous 2° × 2° grid resolution reconstruction by [START_REF] Herold | Middle Miocene tectonic boundary conditions for use in climate models[END_REF] that the authors modified to take into account recently published paleo-topography information.

Details on the method used to reconstruct each paleo DEM can be found in the corresponding publications and here we only provide a summary of the method.

Generally speaking, paleo DEMs are constructed by estimating the topographic resultant of past tectonic settings based on comparison with their modern equivalent [START_REF] Ziegler | Paleogeographic interpretation: With an example from the Mid-Cretaceous[END_REF]. The elevation is defined along contour lines and each grid cell corresponds to a range of elevation and not to a definite value. Each paleo DEM is further corrected using the position of known shorelines or any independent paleo-altitude estimates (paleo-flora, geochemistry, etc.) [START_REF] Markwick | Palaeo-digital elevation models for use as boundary conditions in coupled ocean-atmosphere GCM experiments: a Maastrichtian (late Cretaceous) example[END_REF][START_REF] Markwick | The palaeogeographic and palaeoclimatic significance of climate proxies for data-model comparisons[END_REF]. Finally, a gridded, discrete DEM is obtained through interpolation of the contour lines [START_REF] Herold | A suite of early Eocene (~55 Ma) climate model boundary conditions[END_REF]. The uncertainty associated to these models are difficult to estimate and vary due to the amount of paleo-elevation data available for each period and to the method J o u r n a l P r e -p r o o f use to integrate those data in the models and interpolate them [START_REF] Markwick | Palaeo-digital elevation models for use as boundary conditions in coupled ocean-atmosphere GCM experiments: a Maastrichtian (late Cretaceous) example[END_REF]. For example, [START_REF] Herold | Middle Miocene tectonic boundary conditions for use in climate models[END_REF] published a compilation of paleo-altitude estimates and their uncertainty for the Tibetan plateau and the Andes during the Miocene and Pliocene. Those error margins are generally higher than 500 m and up to 2000 m for the Andes. However, in this study, paleo-elevation data are not used to establish the exact altitude of ranges rather to derive trends in the evolution of the global hypsometry which likely correspond to trends in the complexity of the global topography.

Results

Oxygen

The oxygen isotope composition of paleosols is reported as frequency diagrams along the stratigraphy column (Fig. 2). Diagrams were build using the DensityPlotter program [START_REF] Vermeesch | On the visualisation of detrital age distributions[END_REF] and a Gaussian kernel distribution function. Peaks in the distribution of data are derived from the kernel analysis.

The major peak in the Lower Cretaceous, Upper Cretaceous and Paleogene  18 O distributions is near identical centered on (+22 ± 0.5)‰, although the low number of Lower Cretaceous data makes for less robust statistics. The Cretaceous data possibly display a bimodal distribution with a sub-peak around +10‰ in the Lower Cretaceous and a sub-peak around +16.7‰ in the Upper Cretaceous. Actually, the Lower Cretaceous minor peak corresponds to data obtained from samples collected in southern Australia at a very high paleolatitude of 75°S [START_REF] Gregory | Oxygen isotopic composition of carbonate concretions from the lower Cretaceous of Victoria, Australia: implications for the evolution of meteoric waters on the Australian continent in a paleopolar environment[END_REF].

The Paleogene distribution contains a minor peak at (+17.1 ± 0.5)‰ corresponding to a series of samples collected in the Oligocene Upper John Day Formation in Oregon J o u r n a l P r e -p r o o f [START_REF] Retallack | Glacial-interglacial-scale paleoclimatic change without large ice sheets in the Oligocene of central Oregon[END_REF]. The authors correlate the low  18 O values to cyclic cold periods.

Such low values are also reported from the Eocene of Wyoming (USA), and again interpreted as cyclic shifts in seasonal distribution of precipitations inducing increases in soil water content and correlative decrease in  18 O values [START_REF] Clyde | Lining Wasatchian/Bridgerian boundary to the Cenozoic Global Climate Optimum: new magnetostratigraphic and isotopic results from South Pass, Wyoming[END_REF]. Finally, a few low  18 O values are reported from the Eocene of Tibet, interpreted as associated to low temperature, high altitude environments (Hoke et al., 2014b) A peak at (+22 ± 0.5)‰ is also observed in the Quaternary distribution; however the main peak corresponds to higher  18 O values (at +25‰). This 3‰ difference, which might explain the wide distribution in the Neogene data, also matches the 3‰ increase in the  18 O values of deep-sea foraminifera during the same period, generally considered as reflecting the development of polar ice-caps and the cooling of deep-sea waters [START_REF] Lear | Cenozoic deep-sea temperatures and global ice volumes from Mg/Ca in benthic foraminiferal calcite[END_REF][START_REF] Zachos | Trends, rhythms, and aberrations in global climate 65 Ma to Present[END_REF]Billups and Schrag, 2002) (Fig. 2). A notable feature of the Quaternary dataset is the occurrence of tens of  18 O values (above + 30‰).

Carbon

The distribution of the  13 C values is largely unimodal from the Cretaceous to the Neogene, although a hint of bimodality occurs in the Lower Cretaceous data (Fig. 2).

However, a large number of the high  13 C Lower Cretaceous values (up to +10‰) were J o u r n a l P r e -p r o o f mainly obtained from the Otway and Strzelecki ranges in Australia which show a strong data dispersion and should thus be considered with care [START_REF] Gregory | Oxygen isotopic composition of carbonate concretions from the lower Cretaceous of Victoria, Australia: implications for the evolution of meteoric waters on the Australian continent in a paleopolar environment[END_REF]. Unlike in the oxygen data, the major peak of the distribution varies with time, from -6.9‰ in the Lower Cretaceous, decreasing to -9.3‰ and -9.1‰ in the Upper Cretaceous -Paleogene period then increasing to -6.6‰ in the Neogene. The only remarkable exception are the  13 C values associated to the Paleocene -Eocene transition Thermal Maximum (PETM) that form a secondary peak around -14‰ in the Paleogene distribution [START_REF] Bowen | Refined isotope stratigraphy across the continental Paleocene-Eocene boundary on Polecat Bench in the northern Bighorn Basin[END_REF][START_REF] Koch | Carbon and oxygen isotope records from paleosols spanning the Paleocene-Eocene boundary, Bighorn Basin, Wyoming[END_REF]. These low  13 C values have been interpreted as resulting from the massive release of carbon from marine methane hydrates during the thermal maximum (Dickens et al., 1997;[START_REF] Bains | Mechanisms of climate warming at the end of the Paleocene[END_REF][START_REF] Beerling | Increased terrestrial carbon storage across the Palaeocene-Eocene boundary[END_REF].

The Quaternary distribution is bimodal with peaks at -6.1‰ and -1.4‰. An increase in Due to the relatively limited number of oxygen and carbon isotope data available for the Cretaceous period, we restricted the visualization of the data in the  13 C vs.  18 O diagram to the Paleogene -Quaternary time-range (Fig. 3). Data clusters, labelled A to E in Fig. 3, were obtained using a gaussian kernel density function: the occurrence of a cluster is defined by a peak in the density of data. Although the distribution of data within a cluster may not be homogeneous, we considered that the center of the cluster corresponds to the position of the highest density.

J o u r n a l P r e -p r o o f

Most of the Paleogene data plot within a very narrow range, forming a dense cluster (labelled "A" on Fig. 3). Two smaller clusters (A' and A") are visible, associated to specific time-periods. Cluster A' with low  18 O values but  13 C values comparable to cluster A, corresponds to the cyclic colder and/or wetter periods recorded in the USA or Tibet [START_REF] Clyde | Lining Wasatchian/Bridgerian boundary to the Cenozoic Global Climate Optimum: new magnetostratigraphic and isotopic results from South Pass, Wyoming[END_REF][START_REF] Retallack | Glacial-interglacial-scale paleoclimatic change without large ice sheets in the Oligocene of central Oregon[END_REF]Hoke et al., 2014b). Cluster A" with low  13 C values but  18 O values comparable to cluster A corresponds to PETM-related data.

Finally, some outliers are distributed into a slightly wider region of the graph with an incipient cluster (B) showing higher  18 O values in relation either with evidence of increased aridity or increased hypsometry of the ground-water source region [START_REF] Clyde | Lining Wasatchian/Bridgerian boundary to the Cenozoic Global Climate Optimum: new magnetostratigraphic and isotopic results from South Pass, Wyoming[END_REF][START_REF] Alonso-Zarza | Cenozoic calcretes from the Teruel graben, Spain: microstructure, stable isotope geochemistry and environmental significance[END_REF].

The Neogene data form a wide cloud of points with three clusters. [START_REF] Lee | Stable isotopic composition of pedogenic carbonates of the Early Cretaceous Shimonoseki Subgroup, western Honshu, Japan[END_REF][START_REF] Robinson | Atmospheric pCO2 and depositional environment from stable-isotope J o u r n a l P r e -p r o o f 2 geochemistry of calcrete nodules (Barremian, Lower Cretaceous, Wealden Beds, England)[END_REF][START_REF] Huang | Early Cretaceous atmospheric pCO2 levels recorded from pedogenic carbonates in China[END_REF]. Recent multi-proxy compilations have shown that pCO2 varied largely during the Paleogene. It was variable during the Paleocene with mean values comparable to the present-day ones and much higher during the Eocene with a peak in global warmth during the Ypresian [START_REF] Beerling | Convergent Cenozoic CO2 history[END_REF][START_REF] Hyland | Coupled CO2-climate response during the early Eocene climatic optimum[END_REF]. These conditions likely explain the spread in  13 C values between about -16‰ and 0‰ as the minor peak at -14‰ is clearly related to the PETM.

The pCO2 being comparatively low during the Neogene, the emergence of high  13 C values for that period and the well-defined peak at about -1.4‰ (with data reaching up to about +8‰) for the Quaternary data is largely explained by the Late Miocene rise of C4-dominated ecosystems, with higher- 13 C values [START_REF] Quade | Expansion of C4 grasses in the Late Miocene of northern Pakistan: evidence from stable isotopes of paleosols[END_REF]Fox and Koch, 2004;Edwards et al., 2010;[START_REF] Strömberg | Evolution of grasses and grassland ecosystems[END_REF]. The distribution of the Quaternary  13 C data is thus, at first order, dominated by the C3 (major peak in distribution) and C4 (minor peak) plants-dominated environments (Fig. 2). However, unless considering that all the ecosystems that produced the analyzed paleosols contained a significant proportion of C4 plants, this parameter alone does not explain the complete disappearance of cluster (A) in the  13 C vs  18 O plot (Fig. 3). of the Antarctic Ice cap and of more ephemeral ice in the Arctic [START_REF] Tripati | Evidence for ephemeral middle Eocene to early Oligocene Greenland glacial ice and pan-Arctic sea ice[END_REF], followed by the late Miocene -Pliocene extension of Arctic glaciation [START_REF] Larsen | ODP Leg 152 Scientific Party, Seven million years of glaciation in Greenland[END_REF][START_REF] Helland | Surface textural analysis of quartz sand grains from ODP Site 918 off the southeast coast of Greenland suggests glaciation of southern Greenland at 11 Ma[END_REF], and (2) the Oligocene -Miocene rise of several large mountain ranges. These reliefs increased the number and size of orographic barriers, disrupting the atmospheric circulation.

The Neogene -Quaternary period is marked by a general increase of the  18 O values of pedogenic carbonates (Fig. 2). In the oceanic realm, the Oligocene and Late Miocene -Quaternary global cooling phases induced a comparable increase in the  18 O value of deep-sea foraminifera (Fig. 2; [START_REF] Zachos | Trends, rhythms, and aberrations in global climate 65 Ma to Present[END_REF]. Unless considering that, during the Late Miocene -Quaternary period, the global ocean was isotopically unbalanced due to a large amount of low  18 O water stored in the polar ice-caps and permafrost soils, cooler global temperatures should lead to lower  18 O rainfall values and therefore to lower  18 O values in paleosol carbonates. For example, this temperature effect is put forward to explain the low  18 O values registered in the Early Cretaceous, high-latitude paleosols of southern Australia [START_REF] Gregory | Oxygen isotopic composition of carbonate concretions from the lower Cretaceous of Victoria, Australia: implications for the evolution of meteoric waters on the Australian continent in a paleopolar environment[END_REF]) (Fig. 2). However, cooler temperatures should also increase the CaCO3 -H2O fractionation factor, leading to an increase in the  18 O values of paleosol carbonates [START_REF] Cerling | The stable isotopic composition of modern soil carbonate and its relationship to climate[END_REF]. This effect might participate to the increase of  18 O values during the Neogene and Quaternary (Figs. 2 and3).

Although some mountain ranges such as the North American Cordillera existed during the Cretaceous [START_REF] Wernicke | Tectonomagmatic evolution of Cenozoic extension in the North American Cordillera[END_REF][START_REF] Yonkee | Tectonic evolution of the Sevier and Laramide belts within the North American Cordillera orogenic system[END_REF], global hypsometry increased during the Neogene with the formation or enhanced uplift of mountain ranges such as the Andes [START_REF] Hoke | Paleosurfaces, paleoelevation, and the mechanisms for the late Miocene topographic development of the Altiplano plateau[END_REF], the increased uplift and spreading of the Tibetan plateau [START_REF] Tapponnier | Oblique stepwise rise and growth of the Tibet Plateau[END_REF][START_REF] Kirby | Late Cenozoic evolution of the eastern margin of the Tibetan Plateau: inferences from 40 Ar/ 39 Ar and (U-Th)/He thermochronology[END_REF][START_REF] Liu-Zeng | Quantifying landscape differences across the Tibetan plateau: Implications for topographic relief evolution[END_REF][START_REF] Cheng | Source to sink relation between the eastern Kunlun Range and the Qaidam Basin, northern Tibetan Plateau, during the Cenozoic[END_REF], the topographic growth of the Tian Shan, Altai and Sayan ranges in central J o u r n a l P r e -p r o o f 1 2

Asia [START_REF] Jolivet | Mesozoic and Cenozoic tectonic history of the Central Chinese Tian Shan: Reactivated tectonic structures and active deformation[END_REF][START_REF] Jolivet | Geomorphic Mesozoic and Cenozoic evolution in the Oka-Jombolok region (East Sayan ranges, Siberia)[END_REF](Jolivet et al., , 2018a)), the rise of the Alps [START_REF] Schmid | Geophysicalgeological transect and tectonic evolution of the Swiss-Italian Alps[END_REF][START_REF] Willett | Messinian climate change and erosional destruction of the Central European Alps[END_REF][START_REF] Labaume | Tectonic control on diagenesis in a foreland basin: combined petrologic and thermochronologic approaches in the Grès d'Annot basin (Late Eocene -Early Oligocene, French-Italian external Alps)[END_REF] or the formation of the Southern Alps [START_REF] Tippett | Geomorphic evolution of the Southern Alps, New Zealand[END_REF][START_REF] Chamberlain | Topographic development of the Southern Alps recorded by the isotopic composition of authigenic clay minerals, South Island, New Zealand[END_REF](Fig. 4). These new reliefs increased the number and size of orographic barriers, disrupting the atmospheric circulation and leading to the development of monsoon-type climates and the formation of rain shadows [START_REF] Broccoli | The effects of orography on midlatitude northern hemisphere dry climates[END_REF][START_REF] Dettman | Uplift-driven climate change at 12 Ma: a long δ 18 O record from the NE margin of the Tibetan plateau[END_REF][START_REF] Harris | The elevation history of the Tibetan Plateau and its implications for the Asian monsoon[END_REF][START_REF] Caves | Aridification of Central Asia and uplift of the Altai and Hangay Mountains, Mongolia: Stable isotope evidence[END_REF]. Although the exact relation between the Himalayan monsoon and the aridification of Central Asia remains debated (e.g. [START_REF] Licht | Asian monsoons in a late Eocene greenhouse world[END_REF], it has, for example, been recently shown that loess deposits started to form during the latest Eocene in the central part of the Rocky Mountains (North America) in response to enhanced uplift of the range. Aridification was further increased by the global climate cooling at the Eocene-Oligocene Transition but its onset seems indeed related to orographic processes (Fan et al., 2020). Central Asia provides a good example of the isotopic effect of relief building. In that region, two phenomena are acting to increase the  18 O values of paleosol carbonates: the low- 18 O moisture evaporated from the Indian Ocean to the south is blocked by the Himalayas and rainfalls are mainly sourced from high- 18 O moisture transported by the Westerlies [START_REF] Bershaw | Cenozoic evolution of the Pamir plateau based on stratigraphy, zircon provenance, and stable isotopes of J o u r n a l P r e -p r o o f Journal Pre-proof 1 8 foreland basin sediments at Oytag (Wuyitake) in the Tarim Basin (West China)[END_REF][START_REF] Caves | Role of the westerlies in Central Asia climate over the Cenozoic[END_REF]; in parallel, aridity increased during the Late Paleogene -Quaternary period [START_REF] Bosboom | Aridification in continental Asia after the Middle Eocene Climatic Optimum (MECO)[END_REF], which led to stronger evaporation and to an increase in  18 O values of soil water.

We thus suggest that the global increase in hypsometry during the Late Paleogene -Quaternary period, leading to enhanced regional aridification due to rain shadow effects is registered as a first order signal in the evolution of the isotopic composition of carbonate paleosols. The parallel shift towards higher  18 O values in deep-sea foraminifera and pedogenic carbonates during the Quaternary remains to be explored further. We acknowledge that the parallel deviation of both dataset could be fortuitous J o u r n a l P r e -p r o o f 1 3 but cannot ignore the possibility that, at least for the Quaternary period, both signals record modification in oceanic water oxygen isotopic ratio.

Some examples of second order trends

Second order signals, limited to a specific period of time and/or to a specific locality can also be derived from the present global survey. Some of these are illustrated below despite not being always completely understood.

The first order influence of topography and associated enhanced aridity can be blurred by local effects. A first group of parameters tends to decrease the  18 O values such as the decrease in  18 O values of rainfall with altitude [START_REF] Poage | Empirical relationships between elevation and the stable isotope composition of precipitation and surface waters: considerations for studies of paleoelevation change[END_REF], the mixing between rainfall water and river water coming from high altitude orographic rainfalls [START_REF] Charreau | A high-resolution stable isotopic record from the Junggar Basin (NW China): Implications for the paleotopographic evolution of the Tianshan Mountains[END_REF]Jolivet et al., 2018b) or the development of large freshwater lakes (Jolivet et al., 2018b). On the other hand, increasing evaporation tends to increase the oxygen isotopic composition towards higher values. In some hyper-arid regions such as the Atacama desert, the effects of extreme evaporation makes for carbonates  18 O values incompatible with those expected from carbonates formed in isotopic equilibrium with rainfall water [START_REF] Quade | Soils at the hyperarid margin: The isotopic composition of soil carbonate from the Atacama Desert, Northern Chile[END_REF]. In the same regions, rapid evaporation of rain water implies that carbonates form close or at the surface, in isotopic equilibrium with the atmospheric CO2 and not with the soil CO2 [START_REF] Quade | Soils at the hyperarid margin: The isotopic composition of soil carbonate from the Atacama Desert, Northern Chile[END_REF]. This hyper-aridity likely explains the position of the Quaternary samples having both the highest  18 O and  13 C values in Fig. 3. Similarly, in C3 dominated ecosystems, the  13 C value of paleosol carbonates increases with increasing hydric stress (and the coeval decrease in soil respiration capacities) [START_REF] Kohn | Carbon isotope compositions of terrestrial C3 plants as indicators of (paleo)ecology and (paleo)climate[END_REF]. These secondary parameters likely explain part of the spread in  18 O and  13 C values observed for the Neogene and Quaternary periods (Fig. 2).

J o u r n a l P r e -p r o o f 1 4

As expected from theoretical models (e.g. [START_REF] Cerling | Stable carbon and oxygen isotopes in soil carbonates. Climate Change in Continental Isotopic Records[END_REF], the Quaternary mean  18 O value of each individual dataset shows a weak negative correlation with absolute latitude within the documented range of 4°-45° (Fig. 5a). Between 25° and 40° the large spread in the data is probably related to local variations in evaporation and rainfall following the topographic factors described above. However, the theoretical relationship between the  18 O values and latitude is only observed in the Quaternary dataset, not for the other periods. The Quaternary mean  13 C values show a positive correlation with latitude between 4° and 30° possibly linked to the increase in aridity and relative proportion of C3 and C4 plants in the ecosystems (Fig. 5b). Actually, altitude, by influencing the local climate (especially the mean temperature of the warmest months), also plays a role in the competition between C4 and C3 plants [START_REF] Cotton | Multi-proxy evidence for tectonic control on the expansion of C4 grasses in northwest Argentina[END_REF][START_REF] Hyland | Late Miocene rise and fall of C4 grasses in the western United States linked to aridification and uplift[END_REF]. Above 30° latitude, the mean  13 C values in the Quaternary datasets are largely spread, again probably in response to the impact of complex topography on the ecosystems and soil conditions.

Correlations, positive or negative, exist in the  13 C vs.  18 O plot of individual datasets (Fig. 6a,b). Positive correlations are well documented in the Quaternary and to a lesser extent in the Neogene dataset (see for example the data of [START_REF] Salomons | Isotopic composition of calcrete deposits from Europe, Africa and India[END_REF]; [START_REF] Cerling | An isotopic study of paleosol carbonates from Olduvai gorge[END_REF] or [START_REF] Potts | Stable isotope and 14 C study of biogenic calcrete in a termite mound, Western Cape, South Africa, and its palaeoenvironmental significance[END_REF] for the Quaternary and [START_REF] Latorre | The expansion of C4 grasses and global change in the late Miocene: Stable isotope evidence from the Americas[END_REF] for the Neogene). These trends covering time span of several 10 kyrs to several Myrs are usually explained by climate and ecosystem changes through time: an increase in aridity leads to increased evaporation (inducing higher  18 O values), soil hydric stress (inducing higher  13 C values) and favors C4 plants (again increasing the  13 C values).

Negative correlations are observed in the Quaternary (Yang Wang and Shu-Hui Zheng, 1989), possibly in the Neogene [START_REF] Charreau | A high-resolution stable isotopic record from the Junggar Basin (NW China): Implications for the paleotopographic evolution of the Tianshan Mountains[END_REF] and to a larger extend in the Paleogene [START_REF] Koch | Stable isotope stratigraphy and paleoclimatology of the Paleogene Boghorn Basin (Wyoming, USA)[END_REF][START_REF] Alonso-Zarza | Cenozoic calcretes from the Teruel graben, Spain: microstructure, stable isotope geochemistry and environmental significance[END_REF]) (Fig. 6c-e). Few authors J o u r n a l P r e -p r o o f 5 discussed such negative correlations that remain poorly explored. Only (Alonso-Zarza and [START_REF] Alonso-Zarza | Cenozoic calcretes from the Teruel graben, Spain: microstructure, stable isotope geochemistry and environmental significance[END_REF] proposed that it could be controlled by climate: the driest periods would also be cooler, leading to high  13 C values, associated to a limited variation in  18 O compared to wetter, warmer periods. Finally, some of the Quaternary [START_REF] Alam | The use of oxygen and carbon isotope composition of pedogenic carbonates from Pleistocene palaeosols in NW Bangladesh, as palaeoclimatic indicators[END_REF][START_REF] Alomar | Stable isotope geochemistry of caliche in the Blackwater Draw Formation[END_REF] and Neogene datasets [START_REF] Behrensmeyer | The structure and rate of late Miocene expansion of C4 plants: Evidence from lateral variation in stable isotopes in paleosols of the Siwalik Group, northern Pakistan[END_REF] show a wide range in  13 C values associated to a narrow  18 O range (Fig. 6f,g). Most authors explain the large spread in  13 C values by changes in the proportion of C3 over C4 plants, associated to small variations in climate conditions. However, [START_REF] Alomar | Stable isotope geochemistry of caliche in the Blackwater Draw Formation[END_REF] suggested that changes in  13 C values could also result from fluctuations in the atmospheric component of soil CO2.

Conclusions

The analysis presented here is based on the oxygen and carbon isotope data of pedogenic carbonates of the Cretaceous up to the Quaternary. We show that pedogenic carbonates record long-term, global isotopic signals, complementary to the record of oceanic carbonates. For example, whereas the influence of polar ice-caps from the Late Paleogene (and possibly during the Upper Cretaceous) is recorded in the oceanic  18 O signal, the effects of global continental hypsometry are not. In that respect, continental topography and associated enhanced aridity became a major forcing parameter during the Neogene and Quaternary periods, creating regional-to local-scale climatic conditions leading in turn to contrasted ecosystems. This complex climatic and biologic pattern, associated to the rise of C4 plants during the Neogene, seems to have led to uniquely complex soil carbonates  18 O and  13 C patterns. 6 et al., 2013). The location of the data used in this study is indicated by the encircled numbers. Note that for some of the continental blocks with rapid latitude variations such as India, the position of the data point on the map may not correspond to the paleo-latitude at the deposition time. Data source: Lower Cretaceous -1- [START_REF] Gregory | Oxygen isotopic composition of carbonate concretions from the lower Cretaceous of Victoria, Australia: implications for the evolution of meteoric waters on the Australian continent in a paleopolar environment[END_REF]; 2- [START_REF] Mortazavi | Stable isotope record in pedogenic carbonates in northeast Iran: Implications for Early J o u r n a l P r e -p r o o f 0 Cretaceous (Berriasian -Barremian) paleovegetation and paleoatmospheric P(CO2) levels[END_REF]3, 4-(Huang et al., 2012);5, 6-(Li et al., 2013);7-(Lee and Hisada, 1999); 8- [START_REF] Leier | Stable isotopic results from paleosol carbonate in South Asia: Paleoenvironmental reconstructions and selective alteration[END_REF]9-(Jolivet et al., 2018b); 10- [START_REF] Platt | Lacustrine carbonates and pedogenesis: sedimentology and origin of palustrine deposits from the Early Cretaceous Rupelo Formation, W Cameros Basin[END_REF]; 11- [START_REF] Robinson | Atmospheric pCO2 and depositional environment from stable-isotope J o u r n a l P r e -p r o o f 2 geochemistry of calcrete nodules (Barremian, Lower Cretaceous, Wealden Beds, England)[END_REF]. Upper Cretaceous -1- [START_REF] Nordt | Paleosol barometer indicates extreme fluctuations in atmospheric CO2 across the Cretaceous-Tertiary boundary[END_REF]; 2- [START_REF] Brlek | Stable isotopic ( 13 C and  18 O) signatures of biogenic calcretes marking discontinuity surfaces: a case study from Upper Cretaceous carbonates of cebtral Dalmatia and eastern Istria, Croatia[END_REF]3-(Bojar et al., 2010); 4- [START_REF] Tandon | Palaeoenvironments of the dinosaur-bearing Lameta Beds (Maastrichtian), Narmada Valley, Central India[END_REF]; 5-7- [START_REF] Heilbronn | Stable isotope characterization of pedogenic and lacustrine carbonates from the Chinese Tian Shan: Constraints on the Mesozoic-Lower Cenozoic palaeoenvironmental evolution[END_REF]Jolivet et al., 2018);8-(De Pelsmaeker et al., 2018);9-(Leier et al., 2009); 10- [START_REF] Suguio | Composição química e isotópica dos calcários e ambiente de sedimentação da formação Bauru[END_REF]11-(Dworkin et al., 2005); 12- [START_REF] Gao | Midlatitude terrestrial climate of East Asia linked to global climate in the Late Cretaceous[END_REF]; 13- [START_REF] Sandler | Estimates of atmospheric CO2 levels during the mid-Turonian derived from stable isotope composition of paleosol calcite from Israel[END_REF]); 14- [START_REF] Ghosh | Palaeoclimate and palaeovegetation in central India during the Upper Cretaceous based on stable isotope composition of the palaeosol carbonates[END_REF]. [START_REF] Koch | Stable isotope stratigraphy and paleoclimatology of the Paleogene Boghorn Basin (Wyoming, USA)[END_REF][START_REF] Koch | Carbon and oxygen isotope records from paleosols spanning the Paleocene-Eocene boundary, Bighorn Basin, Wyoming[END_REF]; 3- (Jolivet et al., 2018b); 4- [START_REF] Macaulay | The sedimentary record of the Issyk Kul basin, Kyrgyzstan: climatic and tectonic inferences[END_REF]; 5- [START_REF] Hellwig | Late Oligocene to early Miocene humidity change recorded in terrestrial sequences in the Ili Basin (south-eastern Kazakhstan, Central Asia)[END_REF]6, 7-(Jolivet et al., 2018b); 8- [START_REF] Bowen | Age and correlation of fossiliferous Late Paleocene-Early Eocene strate of the Erlian Basin, Inner Mongolia, China[END_REF]9-(Gao et al., 2015); 10- (Hoke et al., 2014);11-(Alonso-Zarza and Arenas, 2004;[START_REF] Parcerisa | Calcretes, oncolites, and lacustrine limestones in Upper Oligocene alluvial fans of the Montgat area (Catalan Coastal Ranges, Spain)[END_REF]; 12- [START_REF] Garzione | Rise of the Andes[END_REF]; 13- [START_REF] Sinha | New atmospheric pCO2 estimates from paleosols during the late Paleocene/early Eocene global warming interval[END_REF]); 14- [START_REF] Caves | Aridification of Central Asia and uplift of the Altai and Hangay Mountains, Mongolia: Stable isotope evidence[END_REF]; 15- [START_REF] Clyde | Lining Wasatchian/Bridgerian boundary to the Cenozoic Global Climate Optimum: new magnetostratigraphic and isotopic results from South Pass, Wyoming[END_REF][START_REF] Hyland | Coupled CO2-climate response during the early Eocene climatic optimum[END_REF]; 16- [START_REF] Retallack | Glacial-interglacial-scale paleoclimatic change without large ice sheets in the Oligocene of central Oregon[END_REF]. Neogene: 1-(Fox and Koch, 2004);2-(Fox and Koch, 2004;Fox et al., 2012);3-(Mack et al., 1994); 4- [START_REF] Ghosh | Rapid uplift of the Altiplano revealed through 13 C-18 O bonds in paleosol carbonates[END_REF]; 5- [START_REF] Latorre | The expansion of C4 grasses and global change in the late Miocene: Stable isotope evidence from the Americas[END_REF][START_REF] Kleinert | Climate change in response to orographic barrier uplift: Paleosol and stable isotope evidence from the late Neogene Santa María basin, northwestern Argentina[END_REF]; 6- [START_REF] Jordan | Development of the Miocene Manantiales foreland basin, Principal Cordillera, San Juan, Argentina[END_REF][START_REF] Giambiagi | Los depositos Neogenos de la region del Rio Palomares, Cordillera Principal de Mendoza[END_REF][START_REF] Irigoyen | Magnetostratigraphy of Neogene Andean foreland-basin strata, lat 33°S, Mendoza Province, Argentina[END_REF]Hoke et al., 2014);7-(Alonso-Zarza and Arenas, 2004;[START_REF] Huerta | Calcrete and palustrine assemblages on a distal alluvialfloodplain: A response to local subsidence (Miocene of the Duero basin, Spain)[END_REF]Hoke et al., 2014); 8- [START_REF] Quade | Stable isotopic evidence from paleosol carbonates and fossil teeth in Greece for forest or woodlands over the past 11 Ma[END_REF] [START_REF] Cerling | An isotopic study of a fluvial-lacustrine sequence: the Plio-Pleistocene Koobi Fora sequence, East Africa[END_REF][START_REF] Wynn | Paleosols, stable carbon isotopes, and paleoenvironmental interpretation of Kanapoi, Northern Kenya[END_REF][START_REF] Wynn | Influence of Plio-Pleistocene aridification on human evolution: Evidence from paleosols of the Turkana Basin, Kenya[END_REF]Cerling, 2011;[START_REF] Levin | Paleosol carbonates from the Omo Group: Isotopic records of local and regional environmental change in East Africa[END_REF][START_REF] Levin | Compilation of East Africa soil carbonate stable isotope data[END_REF]; 10- [START_REF] Macaulay | The sedimentary record of the Issyk Kul basin, Kyrgyzstan: climatic and tectonic inferences[END_REF][START_REF] Hellwig | Late Oligocene to early Miocene humidity change recorded in terrestrial sequences in the Ili Basin (south-eastern Kazakhstan, Central Asia)[END_REF]11-(Charreau et al., 2012);12-(Heilbronn et al., 2015;[START_REF] Caves | Late Miocene uplift of the Tian Shan and Altai and reorganization of Central Asia climate[END_REF]Jolivet et al., 2018b);13-(Caves et al., 2014);14-(Kaakinen et al., 2006); 15- (Hoke et al., 2014); 16- [START_REF] Quade | Expansion of C4 grasses in the Late Miocene of northern Pakistan: evidence from stable isotopes of paleosols[END_REF][START_REF] Behrensmeyer | The structure and rate of late Miocene expansion of C4 plants: Evidence from lateral variation in stable isotopes in paleosols of the Siwalik Group, northern Pakistan[END_REF]; 17- [START_REF] Aronson | Hominid environments at Hadar from paleosol studies in a framework of Ethiopian climate change[END_REF]Cerling, 2011);18-(Cerling et al., 1991b;[START_REF] Kingston | Stable isotopic evidence for hominid paleoenvironments in East Africa[END_REF]. [START_REF] Schlesinger | The formation of caliche in soils of the Mojave Desert, California[END_REF][START_REF] Liu | Stable carbon and oxygen isotopes of pedogenic carbonates, Ajo Mountains, southern Arizona: implications for paleoenvironmental change[END_REF]3-(Mack et al., 1994;[START_REF] Deutz | Morphology and isotope heterogeneity of Late Quaternary pedogenic carbonates: Implications for paleosol carbonates as paleoenvironmental proxies[END_REF]; 4- [START_REF] Alomar | Stable isotope geochemistry of caliche in the Blackwater Draw Formation[END_REF]Fox and Koch, 2004;Fox et al., 2012); 5- [START_REF] Kleinert | Climate change in response to orographic barrier uplift: Paleosol and stable isotope evidence from the late Neogene Santa María basin, northwestern Argentina[END_REF][START_REF] Quade | Soils at the hyperarid margin: The isotopic composition of soil carbonate from the Atacama Desert, Northern Chile[END_REF]6, 7-(Suguio et al., 1975); 8- [START_REF] Ringrose | Origins of strandline duricrust around the Makgadikgadi Pans (Botswana Kalahari) as deduced from their chemical and isotope composition[END_REF]9-(Cerling and Hay, 1986;[START_REF] Sikes | Isotopic study of Pleistocene paleosols from the Olorgesailie Formation, southern Kenya rift[END_REF][START_REF] Plummer | Research on Late Pliocene Oldowan sites at Kanjera South, Kenya[END_REF]; 10- [START_REF] Cerling | An isotopic study of a fluvial-lacustrine sequence: the Plio-Pleistocene Koobi Fora sequence, East Africa[END_REF][START_REF] Wynn | Influence of Plio-Pleistocene aridification on human evolution: Evidence from paleosols of the Turkana Basin, Kenya[END_REF][START_REF] Quinn | Paleogeographic variations of pedogenic carbonate  13 C values from Koobi Fora, Kenya: implications for floral compositions of Plio-Pleistocene hominin environments[END_REF][START_REF] Levin | Paleosol carbonates from the Omo Group: Isotopic records of local and regional environmental change in East Africa[END_REF][START_REF] Levin | Environment and climate of early human evolution[END_REF]; 11-14- [START_REF] Salomons | Isotopic composition of calcrete deposits from Europe, Africa and India[END_REF]; 15- [START_REF] Salomons | Isotopic composition of calcrete deposits from Europe, Africa and India[END_REF]Eren, 2011;[START_REF] Kaplan | Mineralogical, geochemical and isotopic characteristics of Quaternary calcretes in the Adana region, southern Turkey: Implications on their origin[END_REF]; 16- (Jolivet et al., 2018b); 17- [START_REF] Rowe | Cold' stage formation of calcrete nodules in the Chinese Loess Plateau: evidence from U-series dating and stable isotope analysis[END_REF][START_REF] Wang | A 25 m.y. isotopic record of paleodiet and environmental change from fossil mammals and paleosols from the NE margin of the Tibetan Plateau[END_REF]; 18- (Wang and Zheng, 1989;[START_REF] Wang | A 25 m.y. isotopic record of paleodiet and environmental change from fossil mammals and paleosols from the NE margin of the Tibetan Plateau[END_REF]; 19- [START_REF] Alam | The use of oxygen and carbon isotope composition of pedogenic carbonates from Pleistocene palaeosols in NW Bangladesh, as palaeoclimatic indicators[END_REF]; 20- [START_REF] Srivastava | Paleoclimatic implications of pedogenic carbonates in Holocene soils of the Gangetic Plains, India[END_REF][START_REF] Sinha | Calcretes from a Late Quaternary interfluve in the Ganga Plains, India: Carbonate types and isotopic systems in a monsoonal setting[END_REF]; 21- [START_REF] Salomons | Isotopic composition of calcrete deposits from Europe, Africa and India[END_REF][START_REF] Andrews | Do stable isotope data from calcrete record Late Pleistocene monsoonal climate variation in the Thar desert of India?[END_REF][START_REF] Achyuthan | Petrologic analysis and geochemistry of the Late Neogene -Early Quaternary hardpan calcretes of Western Rajasthan[END_REF][START_REF] Dhir | Multiple episodes of aggradation and calcrete formation in Late Quaternary aeolian sands, Central Thar desert, Rajasthan, India[END_REF]; 22- [START_REF] Quade | Expansion of C4 grasses in the Late Miocene of northern Pakistan: evidence from stable isotopes of paleosols[END_REF][START_REF] Achyuthan | Geochemistry of calcretes (calcic palaeosols and hardpan), Coimbatore, Southern India: Formation and paleoenvironment[END_REF][START_REF] Dar | Isotopic and micromorphological studies of Late Quaternary loess-paleosol sequences of the Karewa Group: Inferences for paleoclimate of Kashmir Valley[END_REF]; 23- [START_REF] Magaritz | Calcium carbonate nodules in soils: 18 O/ 16 O and 13 C/ 12 C ratios and 14 C contents[END_REF][START_REF] Potts | Stable isotope and 14 C study of biogenic calcrete in a termite mound, Western Cape, South Africa, and its palaeoenvironmental significance[END_REF][START_REF] Achyuthan | Geochemistry of calcretes (calcic palaeosols and hardpan), Coimbatore, Southern India: Formation and paleoenvironment[END_REF]; 24- [START_REF] Aronson | Hominid environments at Hadar from paleosol studies in a framework of Ethiopian climate change[END_REF]; 25- [START_REF] Kingston | Stable isotopic evidence for hominid paleoenvironments in East Africa[END_REF][START_REF] Garrett | Stable isotope paleoecology of Late Pleistocene Middle Stone Age humans from the Lake Victoria basin, Kenya[END_REF]. excluding the data from [START_REF] Gregory | Oxygen isotopic composition of carbonate concretions from the lower Cretaceous of Victoria, Australia: implications for the evolution of meteoric waters on the Australian continent in a paleopolar environment[END_REF] that are clearly affected by a strong latitudinal effect. The deep-sea foraminifera  18 O and  13 C variation curves are from [START_REF] Zachos | Trends, rhythms, and aberrations in global climate 65 Ma to Present[END_REF]. The pictures to the left illustrate various types of paleosols: top, carbonate nodules and bottom, carbonate root cast (pictures M. Jolivet). The time-span of major events (glaciations, mountain uplifts and expansion of C4 flora) are reported, the increasing thickness of the grey envelope representing increases in mountain in uplift rates. The references of the data and the data are reported in Supplementary Table S1, the geographic position of the studies are given on Fig. 1. ~2.8° latitude × 2.8° longitude resolution [START_REF] Sewall | Climate model boundary conditions for four Cretaceous time slices[END_REF] and the Quaternary data have been interpolated on a 2° latitude × 2° longitude using the USGS EROS Archive GTOPO30 database and the GMT software [START_REF] Wessel | Free software helps map and display data[END_REF]

  . The proportion of these low  18 O values tend to decrease after the Oligocene. The Neogene distribution of  18 O values displays a wide peak, almost a plateau, with a central value of (+23 ± 0.5)‰. This broad distribution might correspond to a combination between the (+22 ± 0.5)‰ peak observed in the Cretaceous and Paleogene data and a new population of data with  18 O values around +25‰. Very few  18 O values are above 30‰.



  13 C values seems to start in the Neogene distribution. Interestingly, this increase mirrors the decrease of the  13 C values of the deep-sea foraminifera observed by[START_REF] Zachos | Trends, rhythms, and aberrations in global climate 65 Ma to Present[END_REF] from the Neogene (Fig.2).3.3.  13 C vs.  18 O values.

1

 1 Cluster A might correspond to Paleogene cluster A, however slightly shifted towards lower  18 O values (by about 1.5‰). Cluster B represents the majority of the data. It displays  13 C and  18 O central value higher than cluster A. Its position is similar to that of the incipient cluster B observed in the Paleogene data. The third cluster C has  13 C values generally higher than those of A and B and  18 O values lower than B and similar to slightly higher than A. The differentiation in several clusters is obvious in the Quaternary data: cluster A defined for Paleogene and Neogene data no longer exists, cluster B becomes major with an increase in the central  13 C value and cluster C has largely reduced. Two new clusters (D, E) can be identified, corresponding to an increase in  13 C and  18 O values, respectively. Also new in the Quaternary data set is the rather high number of samples with both high  13 C and  18 O values . Global signals: pCO2, emergence of C4 plants, global cooling and hypsometry Global, long-term isotopic signals depicted above are registered in carbonate-bearing paleosols implying that global forcing parameters have to be invoked. Some of the Early Cretaceous  13 C values (higher than 0‰, Fig. 2, lower right) seem correlated to high pCO2 values

  Besides the emergence of C4 plants, two other main events distinguish the late Paleogene -Quaternary period from the Cretaceous -Early Paleogene that likely influence the isotopic signals. These are (1) the middle Eocene -Oligocene development J o u r n a l P r e -p r o o f 1 1

Figure 1 -

 1 Figure 1-A: Paleogeographic maps of the Lower Cretaceous (bottom) and Upper

Figure 1 -

 1 Figure 1-B: Paleogeographic maps of the Paleocene (bottom, including all Paleogene data)

  ; 9-(Cerling et J o u r n a l P r e -p r o o f 7

Figure 1 -

 1 Figure 1-C: Present-day geographic map (top) simplified from Scotese (2014d) and

Figure 2 :

 2 Figure 2: Kernel density estimation of  18 O (left) and  13 C (right) values for the

Figure 3 : 9 Figure 4 :

 394 Figure 3:  13 C versus  18 O diagrams in plan view (left) and 3D (right) for the Paleogene,

  . (B) Probability density curve of global altitudes above sea level at different periods showing the progressive increase elevation over 3000 m during the Miocene and Quaternary. Cretaceous and Quaternary data are as on Fig. 3A, Early Eocene data from Herold et al. (2014) and middle-Miocene data from Frigola et al. (2018).

Figure 5 :

 5 Figure 5: Distribution of the mean isotopic values of each individual dataset as a function

Figure 6 :

 6 Figure 6:  18 O versus  13 C diagrams of individual samples for various periods illustrating

Figure 1B

 1B Figure 1B

Figure 2

 2 Figure2

Figure 3

 3 Figure3

Figure 4

 4 Figure4

Figure 5

 5 Figure5

Figure 6

 6 Figure6

Acknowledgements

J o u r n a l P r e -p r o o f 6

We would like to thank Ch. Lecuyer for helpful discussions, A. Kaakinen and J. Andrews for providing access to datasets and two reviewers for their very helpful comments and suggestions. Funding for authors salaries was from Centre National de la Recherche Scientifique for M. Jolivet and University Rennes 1 for Ph. Boulvais. 0 Behrensmeyer et al. (2007) showing a wide range of  13 C values associated to a narrow spread in  18 O values.

Data Availability Statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study.

Supplementary Table

 S1: Isotopic data used in this study for the (A) Cretaceous, (B) Paleogene, (C) Neogene, (D) Quaternary. The isotope values are reported using the conventional "" values using VSMOW as the standard for oxygen (which implied recalculation of the delta value when it was reported against PeeDeeBelmenite in the original publication) and VPDB as the standard for carbon. ## indicate values that were not reported in the original publication or values identified by the authors as affected by diagenetic processes.

Declaration of interests

X The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.


André J Arruda¹
email: ajarruda@gmail.com

Fernando A O Silveira¹

Elise Buisson²

Reliability of seed rain estimates A simple standardized protocol to evaluate the reliability of seed rain estimates

Keywords: seed loss, seed rain, seeds sorting, seed trap, trap effectiveness

Seed dispersal has key implications for community dynamics and restoration ecology.

However, estimating seed rain (the number and diversity of seeds arriving in a given area) is challenging, and the lack of standardization in measurement prevents cross-site comparisons. Seed trap effectiveness and accuracy of seed sorting methods are key components of seed rain estimates in need of standardization. We propose and describe a standardized protocol for evaluating the effectiveness of two seed trap types (sticky and funnel traps), and the accuracy of a seed sorting method. We used widely available seeds (arugula, quinoa, sesame and sunflower) to produce a gradient of seed size, weight and color. Proof-of-concept was tested in a tropical grassland, where traps were set for 30 days. Our results suggest that we underestimate dispersal of small seeds (less than 2mm width) that can be easily mistaken for debris and soil particles or that fail to adhere to sticky traps. Seeds on sticky traps may be more vulnerable to removal by wind and rain, whereas seeds in funnel traps are more susceptible to decay. We found no evidence of observer bias on seed sorting for funnel trap samples. However, accuracy on seed sorting for funnel trap samples tended to decline for seeds with less than 2mm width, suggesting a size-dependence in seed retrieval success. Our standardized protocol addressing trap effectiveness and seed sorting methods will increase reliability of data obtained in seed rain studies in grasslands and allow more reliable comparisons between datasets.

Introduction

Seed dispersal studies are vital to understanding plant distribution and community resilience, and they guide conservation and restoration activities [START_REF] Török | Beyond the species pool: modification of species dispersal, establishment, and assembly by habitat restoration[END_REF]. A useful way of studying seed dispersal is to estimate seed rain -i.e. the number and diversity of new seeds reaching a given area (Baskin and Baskin 2014)using seed traps to collect propagules at particular locations, then identifying and counting them.

However, measuring seed rain is challenging, and a lack of methodological standardization persists, compromising the accuracy of seed rain estimates and impairing comparison of data between studies [START_REF] Arruda | How have we studied seed rain in grasslands and what do we need to improve for better restoration[END_REF][START_REF] Wolfe | Seed rain along a gradient of degradation in Caribbean dry forest: Effects of dispersal limitation on the trajectory of forest recovery[END_REF]. Seed rain has long been used by ecologists to address ecological succession and factors limiting regeneration in tropical forests [START_REF] Holl | Factors Limiting Tropical Rain Forest Regeneration in Abandoned Pasture: Seed Rain, Seed Germination, Microclimate, and Soil1[END_REF][START_REF] Saulei | Rain forest seed dynamics during succession at Gogol, Papua New Guinea[END_REF]. In open environments, however, seed dispersal by wind and water run-off poses additional challenges to estimate seed rain. . For example, despite seed rain in temperate grasslands has been relatively well studied, we not only need more research in other grasslands types (e.g. tropical grasslands), but to improve many crucial aspects related to methods standardization and data reporting [START_REF] Arruda | How have we studied seed rain in grasslands and what do we need to improve for better restoration[END_REF]. Determining the effectiveness of seed traps, and of seed sorting methods for samples, is crucial for improving reproducibility, but it is rarely tested in seed rain studies [START_REF] Thompson | A comparison of eight types of mast traps[END_REF][START_REF] Jackel | Diaspore production and the influence of the size of diaspore traps on the quantitative result of seasonal diaspore rain in two calcareous grassland sites[END_REF][START_REF] Kollmann | Notes on seed traps in terrestrial plant communities[END_REF][START_REF] Stevenson | Sample size and appropriate design of fruit and seed traps in tropical forests[END_REF].

Evaluation of seed trap effectiveness involves the evaluation of two processes: trap capacity to capture seeds (seed catch), and trap capacity to retain seeds (seed retention) and avoid seed loss (Box 1; Fig. 1). Additionally, the accuracy of seed sorting methods for trap samples depends not only on seed size-small seeds are harder to findbut also on the ability to separate seed material from debris, which can strongly affect seed retrieval rates [START_REF] Cottrell | Seed rain traps for forest lands: Considerations for trap construction and study design[END_REF]. Knowing the seed retrieval rate of seed sorting is important for determining the influence of seed size, of observer effect, and of sample composition, or more precisely, the color and size of soil particles, debris and litter often present in samples [START_REF] Debussche | Bird-dispersed seed rain and seedling establishment in patchy Mediterranean vegetation[END_REF].

Among other invertebrates, ants are known for their ability to collect large amounts of seeds and can have a major impact on seed trap effectiveness [START_REF] Predavec | Seed removal by rodents, ants and birds in the Simpson Desert, central Australia[END_REF]. Seed decay can vary greatly between seed types and is also modulated by other biotic and abiotic conditions such as pathogens, humidity and the amount of litter/soil accumulated within traps [START_REF] Roberts | Loss of viability and crop yields[END_REF]; Box 1). Additionally, seed loss by wind or water run-off can vary greatly between trap types, seasons and plant communities, thereby influencing seed retrieval rates. Therefore, to maximize seed catch and minimize seed loss in open ecosystems, the use of complementary seed trap types is recommended [START_REF] Chabrerie | Comparison of three seed trap types in a chalk grassland: toward a standardised protocol[END_REF].

Funnel traps can be used to study local seed rain and the transportation of seeds by water run-off [START_REF] Jackel | Diaspore production and the influence of the size of diaspore traps on the quantitative result of seasonal diaspore rain in two calcareous grassland sites[END_REF]. Funnel traps are effective in seed catch, but seed loss to predation and to decay caused by excessive moisture arise as potential problems [START_REF] Schott | A seed trap for monitoring the seed rain in terrestrial communities[END_REF][START_REF] Kollmann | Notes on seed traps in terrestrial plant communities[END_REF][START_REF] Jensen | Species composition of soil seed bank and seed rain of abandoned wet meadows and their relation to above ground vegetation[END_REF]. Sticky traps, in turn, are more suitable for studying wind-dispersed species (Jefferson and Usher 1989). While sticky traps carry a lower risk of seed predation, checking them is often hindered by trapped insects and debris [START_REF] Kollmann | Notes on seed traps in terrestrial plant communities[END_REF]. Both sticky and funnel traps may also bias the seed catch towards larger seeds that are more easily detected by visual assessment, while soft seeds may easily rot, and smooth seeds may be lost through rain or wind action [START_REF] Kollmann | Notes on seed traps in terrestrial plant communities[END_REF][START_REF] Cottrell | Seed rain traps for forest lands: Considerations for trap construction and study design[END_REF]. Despite the current state of knowledge, the influence of seed size and weight on the retention rate of seed traps is still overlooked.

Among the possible methods for sorting seeds in funnel-trap samples, the most effective is direct seed inspection after sieving to separate seeds from debris [START_REF] Kollmann | Notes on seed traps in terrestrial plant communities[END_REF]Cottrel, 2004). Seed identification requires training; however, one's capacity to find and sort seeds also depends on seed traits, such as size and color [START_REF] Martin | Seed identification manual[END_REF][START_REF] Cottrell | Seed rain traps for forest lands: Considerations for trap construction and study design[END_REF]. Considering that results can be biased by differences in one's capacity to find and sort seeds from the samples, it is important to obtain, prior to data interpretation in seed rain studies, an estimate of how many seeds are missed in the sorting procedure. Our goal is to propose and describe a simple standardized protocol to evaluate the effectiveness in seed retention of two types of seed trap (Box 1, Fig. 1), and the accuracy of a seed sorting method in assessing seed rain. The standardized protocol should be run along with every seed rain study using these traps to allow more reliable comparisons between studies. We tested these standardized protocols in a tropical grassland as a proof-of-concept.

Description and implementation

SEED TRAPS

We tested sticky and funnel traps (Fig. 2), which capture complementary processes of seed rain [START_REF] Chabrerie | Comparison of three seed trap types in a chalk grassland: toward a standardised protocol[END_REF] and are the most common traps used to estimate seed rain in grasslands [START_REF] Arruda | How have we studied seed rain in grasslands and what do we need to improve for better restoration[END_REF]. We provide detailed instructions on how these two seed traps can be built using low-cost and readily available material (Appendices S1-S2).

STANDARDIZED PROTOCOL

We used four species: arugula (Eruca sativa), quinoa (Chenopodium quinoa), sesame (Sesamum indicum) and sunflower (Helianthus annuus). Here, the sunflower achenes are called seeds to facilitate the terminology throughout the manuscript. These seeds are available in most market or garden center worldwide and provide variation in size, weight and colors that can be tested across ecosystems (Table 1). To assess seed retention, the number of traps and the length of time that traps should be left in the field can be adapted to each study and grassland type. Killing the seeds before using them in the field is a mandatory step to 1) prevent the seeds from germinating on the seed traps, 2) avoid contamination by pathogens that may be associated with these seeds [START_REF] Godefroid | Effectiveness of dry heat as a seed sterilisation technique: Implications for ex situ conservation[END_REF], 3) prevent invasion of exotic species [START_REF] Estévez | Clarifying values, risk perceptions, and attitudes to resolve or avoid social conflicts in invasive species management[END_REF]. We placed all seeds in a drying oven at 120°C for an hour, as treatments heating seeds above 85°C for more than 8 min have shown to kill most seeds [START_REF] Hess | Microwave soil heating reduces seedling emergence of a wide range of species including invasives[END_REF]. We conducted all seed measurements (e.g. weight and size) after the heat treatment.

On each trap, we gently dropped 10 seeds of each species, totaling 40 seeds per trap (Table 1). On funnel traps, we put all seeds straight into the bag collectors. It is best to run the standardized protocol either during the same season(s) as the study or, if run over one year, during the season in which conditions are most challenging for preservation of the seeds on the traps. For the sticky traps, all samples collected from each trap are examined under magnification. For the funnel traps, bags are collected separately from each trap, and their content washed in a 250-μm sieve to reduce the amount of fine soil particles, then examined under a magnifying glass to count and identify seeds. All seeds are counted and any signs of damage recorded.

To evaluate seed loss during the seed sorting of funnel traps samples, a second experiment examines the sorting accuracy with funnel traps samples. We chose to test the seed sorting accuracy with only funnel trap samples because the traps can accumulate much litter and soil in the field, making it difficult to retrieve seeds. For this test, a given number of seeds of the four species are mixed in soil, in a proportion equal to that commonly found inside the funnel trap bags. The soil used must be taken from the study area to control for color, debris and litter composition. The number of seeds in each sample (with a minimum of 3 and maximum of 30 seeds per species) should be randomized and noted; this number is not known to the observers. A minimum of three previously trained observers then sort the samples, searching for, identifying and counting the seeds. For ethical aspects, observers' anonymity must be respected when collecting and reporting the data.

The proportion of seeds retrieved at the end of the experiments (retrieval success) is obtained by calculating the percentage of seeds retrieved by each observer. Both experiments are analyzed using generalized linear models that assume a quasibinomial distribution and use retrieval success as the response variable. For the seed trap effectiveness experiment, trap type and species are the categorical variables (interaction was tested). For the seed sorting experiment, species and experimenters are the categorical variables (interaction was tested). In both cases, pairwise contrast comparisons with a Tukey adjustment can be run. We here performed these analyses with R (R Core Team, 2018), packages base and emmeans.

PROOF OF CONCEPT

In order to proof-of-concept our protocol, we conducted fieldwork in the southern part of the Espinhaço mountain range, southeastern Brazil (43º 35' W, 19º 17' S). The annual precipitation averages around 1,400 mm, and climate is markedly seasonal, with most rainfall occurring in the hot summers [START_REF] Silveira | Ecology and evolution of plant diversity in the endangered campo rupestre: a neglected conservation priority[END_REF]. We conducted the experiment in March 2017, at the end of the raining season, when high temperatures, strong winds and rainy days prevail, creating the most challenging conditions in the study area. The main vegetation comprises the mountaintop campo rupestre, fire-prone open grasslands that establish on quartzite-derived rocks, with shallow and severely nutrientpoor sandy soils [START_REF] Silveira | Ecology and evolution of plant diversity in the endangered campo rupestre: a neglected conservation priority[END_REF].

We randomly placed six of each type of seed trap on a pristine site (50 m²), and retrieved seeds after a period of one month, as this the most common timeframe used to sample seed rain in grasslands [START_REF] Arruda | How have we studied seed rain in grasslands and what do we need to improve for better restoration[END_REF]. For the second experiment, testing seed sorting accuracy with funnel trap samples, we ran the protocol with three previously trained observers in the laboratory.

Results of the proof-of-concept

In the proof-of-concept experiment, we found no difference between the two trap types in sunflower seed retention, with both performing well (98. 6% for funnel trap and 100% for sticky trap) (Fig. 3). Funnel traps were ineffective in retaining quinoa seeds under the field conditions, while the sticky trap had a good retention rate for quinoa seeds (88.6%; LM quasibinomial, p<0.001; Fig. 3). We found no significant difference in the performance between seed traps for sesame seeds (Fig. 3). Funnel traps performed better than sticky traps in the retention of arugula seeds (41.4% more efficient than sticky traps) (Fig. 3). Quinoa and arugula seeds had the lowest retention rates, with only 1.4% and 42.9% of the arugula seeds on sticky and funnel traps, respectively, and no quinoa seeds retrieved from funnel traps, after one month in the field. Most sesame seeds and sunflower seeds were retrieved from both sticky and funnel traps (> 88%) (Fig. 3).

We found no evidence to support an observer effect (GLM quasibinomial, p>0.05), but, while finding most seeds during seed sorting, there was a slight difference in retrieval success between species, arugula being significantly lower: 88.6% of arugula seeds, 97.9% of quinoa seeds, 96.9% of sesame seeds and 100% of sunflower seeds (Fig. 4; GLM quasibinomial, p<0.001).

Discussion

Improving the accuracy and precision of seed rain estimates is necessary to further our understanding of both seed dispersal and seed limitation, and to support ecological restoration [START_REF] Török | Beyond the species pool: modification of species dispersal, establishment, and assembly by habitat restoration[END_REF]. However, few studies test seed trap effectiveness in open ecosystems [START_REF] Arruda | How have we studied seed rain in grasslands and what do we need to improve for better restoration[END_REF], thus precluding attempts to understand these processes on a global scale. Our results show that, under the tested field conditions, both trap types underperformed for species having seeds smaller than 2mm width, and so that we are underestimating seed dispersal of small seeds. Despite finding no observer bias on seed sorting for funnel trap samples, we found that accuracy tended to decline for seeds under 2mm width size, suggesting that size-dependence in seed retrieval success is more common than previously thought [START_REF] Kollmann | Notes on seed traps in terrestrial plant communities[END_REF].

Despite the lower risk of seed predation with sticky traps, due to the strong glue over the Plexiglas® plate, the seeds on sticky traps are more exposed, and thus more vulnerable to removal by wind and precipitation, than seeds in funnel traps. Sticky traps may also be problematic because insects, dust and litter can easily accumulate on the trap's glue, hindering the visual search for seeds. Traps near the ground are more vulnerable to contaminants, catching large quantities of dust and litter, especially during the rainy season. We believe that the height of our sticky traps (25 cm above the soil) greatly reduced their contamination by soil particles, but it did not prevent contamination by insects. Notably, many of the insects were mere incidental captures rather than active seed predators. In contrast, contamination by insects was negligible for funnel traps. The high loss rates found for quinoa and arugula seeds in funnel traps indicate alarming losses for small seeds in general. The weak structure of the quinoa seed coat can make these seeds more vulnerable to mechanical stress, fluctuations in humidity and temperature, and growth of microorganisms [START_REF] Mohamed-Yasseen | The Role of Seed Coats in Seed Viability[END_REF]. The loss of quinoa seeds are thus probably linked with humidity within the funnel traps and seed decay is likely the main cause of seed loss in funnel traps (seed removal by animals is unlikely due to the shape of the funnel trap). It shows that when reporting results, one should be aware that seed rain may presents diaspores vulnerable to decay resulting in underestimation on seed rain surveys, especially during data collection on rainy seasons.

Seeds with hard seed coats, such as sesame and arugula, are generally long-lived and have high retention rates by funnel traps [START_REF] Priestley | Seed aging[END_REF]. Hard seed coats may negative influence the retention capacity of small seeds on sticky traps, as most arugula seeds were probably washed off by rain or removed by strong winds from the glue.

Despite finding no observer bias on seed sorting for funnel trap samples, we found that accuracy tended to decline with decreasing seed size and for seeds of darker color.

Soils with high content of organic particles, like where we tested the proof-of-concept, may directly impact the accuracy of seed sorting methods because soil particles are similar in color to some seeds; sorting methods should account for this similarity.

Conclusion

Our study clearly demonstrates that the traits of seeds influence their retrieval from seed traps used in seed rain studies. We provide a detailed standardized protocol that can be easily implemented in any seed rain study in grasslands using sticky and funnel traps that can be tested and used in globally distributed experiments [START_REF] Borer | Finding generality in Ecology: a model for globally distributed experiments[END_REF]. When discussing the results of a seed rain study using the proposed protocol, one must offer the caveat that the methodology applied likely underestimates seed rain considering seed traits, traps types and environmental conditions. Under our field conditions, our seed rain study would not allow us to conclude that small, soft seeds cannot be dispersed by water run-off, as they may decay in funnel traps; nor could we infer anything regarding small, dark, smooth seeds, as they can be lost from sticky traps or not found by observers.

Finally, we argue that our standardized protocol addressing trap effectiveness and seed sorting methods will increase reliability of data obtained in seed rain studies in grasslands and allow more reliable comparisons between datasets. Seed catcha property of seed traps that refers to its ability to trap seeds from the seed rain.

The final number of seeds captured by a seed trap is affected by both seed retention and seed loss.

Seed retentiona property of seed traps that refers its capacity to maintain seeds on/in traps after seed catch until seed retrieval.

Seed lossprocess caused by seed predators, pathogens and unknown causes that decreases seed trap effectiveness and produce the final trap sample

Seed decay -the progressive deterioration of the structures and functions of the seed over time, and which will ultimately leads to seed death There are two possible methods for seed sorting in trap samples. The grow-out method involves transferring the collected material to trays in greenhouses and identifying species from growing seedlings. This method is time-and labor-consuming, and underestimates dormant seeds. In the direct seed inspection method, each sample is processed for seed separation, and identification using a magnifying glass. Standardizing seed counting at the seed sorting stage is essential to decrease the likelihood of scoring bias.

Fig. 1 .

 1 Fig. 1. Conceptual framework showing two key stages of seed rain measurements

Fig. 2 .

 2 Fig. 2. (a) Sticky trap. a1: clear Plexiglas® plate (0.0225 m²); a2: sticky gel over a thin

Fig. 3 .

 3 Fig. 3. Retrieval success for four species in two seed trap types over a 30-day period

Fig. 4 .

 4 Fig. 4. Retrieval success on the sorting accuracy test of the funnel trap samples for the

Table 1 :

 1 Seed average width, length and weight for the four species that should be used in the protocol from measurements made from 15 seeds of each species after heat treatment at 120°c for an hour.Seed trap effectivenessthe ability of seed traps to accurately and precisely estimate seed rain. Seed trap effectiveness is determined by seed catch and seed retention.

	Species and family	Weight (mg) Width (mm) Length (mm)	Color
	Arugula (Eruca sativa, Brassicaceae)	2.2±0.0005	1.3±0.1	1.8±0.2	Dark brown
	Quinoa (Chenopodium quinoa, Amaranthaceae)	4.6±0.001	2.1±0.001	2.3±0.2	Whitish
	Sesame (Sesamum indicum, Pedaliaceae)	6.4±0.001	1.9±0.2	5.2±0.3	Pale beige
	Sunflower (Helianthus annuus, Asteraceae)	51.2±0.01	5.4±0.60	10.5±0.65	Pale grey

Acknowledgments

We thank P.A. Junqueira and H.T.S. Rodrigues for assisting in the seed sorting accuracy tests, and M. King for language editing and review. A.J.A. receives a scholarship from CAPES and FAPEMIG and F.A.O.S. receives grants from CNPq and FAPEMIG. This work was also supported by CNRS PICS 2018-2020[RESIGRASS]. The authors declare no conflict of interest.

Authors' contributions

All authors conceived the ideas and designed methodology; A.J.A. and E.B. collected the data; A.J.A. and E.B. analysed the data; A.J.A. led the writing of the manuscript. All authors contributed critically to the drafts and gave final approval for publication.

Supporting Information

Additional Supporting Information may be found in the online version of this article.

Data S1. Sticky traps construction guidelines (Sticky_trap.csv).

Data S2. Funnel traps construction guidelines (Funnel_trap.csv).

Data S2. Funnel traps construction guidelines (Funnel_trap.csv).

Use a PVC pipe measuring 11.4 cm high × 15.0 cm wide (top) × 10 cm long, originally designed for cheese production. This cylindrical plastic structure should have holes, 1 cm in diameter, on the sides and bottom to allow drainage. Attach a conical PVC plastic funnel, 15 cm in diameter, to the top end of the cylindrical plastic structure (approximately 0.0177 m² in area). At the bottom of the funnel, the seeds are caught in a disposable polypropylene bag, with pores smaller than 0.1 mm, fixed with an elastic band to the base of the funnel. This polypropylene bag is originally produced as a disposable hygienic hair cap, and it retains its integrity over the period of exposure in the field, independent of weather conditions (TALGE, Santa Catarina, Brazil).