Edouard Bard

Edouard Bard
Collège de France · CEREGE

About

490
Publications
96,748
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59,882
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Additional affiliations
October 1991 - October 2001
Aix-Marseille Université
Position
  • Professor
October 1991 - present

Publications

Publications (490)
Article
The early Pleistocene was driven by 41 kyr glacial cycles that have been rarely characterized in continental records, especially in South America. Most of long-term records derive from marine records (e.g.sea surface temperatures (SST)) and have been widely used to infer past climate dynamics but implications for the continent have rarely been eval...
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We present the results of a multi-disciplinary investigation on a deciduous human tooth (Pradis 1), recently recovered from the Epigravettian layers of the Grotte di Pradis archaeological site (Northeastern Italian Prealps). Pradis 1 is an exfoliated deciduous molar (Rdm2), lost during life by an 11–12-year-old child. A direct radiocarbon date prov...
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The climate history of the Sahara desert during recent millennia is obscured by the near absence of natural climate archives, hampering insight in the relative importance of southerly (tropical) and northerly (midlatitude) weather systems at submillennial time scales. A new lake sediment record from Ounianga Serir oasis in northern Chad, spanning t...
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Mid-latitude mountain glaciers are sensitive to local summer temperature changes. Chronologies of past glacier fluctuations based on the investigation of glacial landforms therefore allow for a better understanding of natural climate variability at local scale, which is relevant for the assessment of the ongoing anthropogenic climate warming. In th...
Article
Radiocarbon (14C), as a consequence of its production in the atmosphere and subsequent dispersal through the carbon cycle, is a key tracer for studying the Earth system. Knowledge of past 14C levels improves our understanding of climate processes, the Sun, the geodynamo, and the carbon cycle. Recently updated radiocarbon calibration curves (IntCal2...
Preprint
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Mid-latitude mountain glaciers sensitively respond to local summer temperature changes. Chronologies of past glacier fluctuations based on the investigation of glacial landforms therefore allows for a better understanding of warm-season climate variability at local scale. In this study, we focus on the Holocene, the current interglacial of the last...
Article
This study presents a new precise radiocarbon chronology for the World Heritage site of Sarvestan (SW Iran). The monument is a key construction in the history of architecture because it is a typical Sasanian construction built during the late Sasanian or early Islamic period. Previous attempts to date the monument have suggested the ages ranging fr...
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We assess the methodology of the so-called 14C plateau tuning (PT) technique used to date marine sediment records and determine 14C marine reservoir ages (MRAs) as recently reviewed by Sarnthein et al. (2020). The main identified problems are linked to the assumption of constant MRA during 14C age plateaus; the lack of consideration of foraminifera...
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RI‐OH′ and RI‐OH (ring index of hydroxylated tetraethers) are two novel organic paleothermometers which could either complement or replace more established paleothermometric proxies, such as UK′37 (C37 ketone unsaturation ratio) and TEX86 (TetraEther indeX of tetraethers consisting of 86 carbon atoms). Despite a few promising attempts, the paleothe...
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La découverte d’une mandibule néandertalienne dans la grotte du Boquete de Zafarraya en1983, fut à l’origine de l’extraordinaire recherche pluridisciplinaire engagée par Cecilio Barroso-Ruíz et Henry de Lumley et menée par plusieurs équipes espagnoles et françaises, appartenant à différentes universités et institutions scientifiques.
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Sometime during the middle to late Holocene (8.2 ka to ∼ 1850–1900 CE), the Greenland Ice Sheet (GrIS) was smaller than its current configuration. Determining the exact dimensions of the Holocene ice-sheet minimum and the duration that the ice margin rested inboard of its current position remains challenging. Contemporary retreat of the GrIS from i...
Preprint
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As an extended comment on the paper by Sarnthein et al. (2020), we express strong reservations about the methodology of the so-called 14C plateau tuning (PT) technique used to date marine sediment records and its implications on the determination of 14C marine reservoir ages (MRA). The main problems are linked to: the assumption of constant MRA dur...
Preprint
Full-text available
During the middle to late Holocene (8.2 ka BP to present), the Greenland Ice Sheet (GrIS) was smaller than its current configuration. Determining the exact dimensions of the Holocene ice-sheet minimum and the duration that the ice margin rested inboard of its current position remains challenging. Contemporary retreat of the GrIS from its historical...
Article
Short tree-ring series are a recurrent problem in dendroarchaeological studies because they are difficult to match against site and reference chronologies. Young wood posts discovered at the Early Bronze Age pile-dwelling site of Lucone D (Brescia, Italy) show tree-ring series not exceeding 40 rings. Dendrochronological analysis allowed us to cross...
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The radiocarbon (14 C) calibration curve so far contains annually resolved data only for a short period of time. With accelerator mass spectrometry (AMS) matching the precision of decay counting, it is now possible to efficiently produce large datasets of annual resolution for calibration purposes using small amounts of wood. The radiocarbon interc...
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The new radiocarbon calibration curve (IntCal20) allows us to calculate the gradient of the relationship between ¹⁴ C age and calendar age over the past 55 millennia before the present (55 ka BP). The new gradient curve exhibits a prolonged and prominent maximum between 48 and 40 ka BP during which the radiocarbon clock runs almost twice as fast as...
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The concentration of radiocarbon ( ¹⁴ C) differs between ocean and atmosphere. Radiocarbon determinations from samples which obtained their ¹⁴ C in the marine environment therefore need a marine-specific calibration curve and cannot be calibrated directly against the atmospheric-based IntCal20 curve. This paper presents Marine20, an update to the i...
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The stratigraphy at Bacho Kiro Cave, Bulgaria, spans the Middle to Upper Palaeolithic transition, including an Initial Upper Palaeolithic (IUP) assemblage argued to represent the earliest arrival of Upper Palaeolithic Homo sapiens in Europe. We applied the latest techniques in 14C dating to an extensive dataset of newly excavated animal and human b...
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The Middle to Upper Palaeolithic transition in Europe witnessed the replacement and partial absorption of local Neanderthal populations by Homo sapiens populations of African origin1. However, this process probably varied across regions and its details remain largely unknown. In particular, the duration of chronological overlap between the two grou...
Conference Paper
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The stable oxygen isotope ratio (δ18O) of planktic foraminifers, the C37 ketone unsaturation ratio (UK′37) and the TetraEther indeX of tetraethers consisting of 86 carbon atoms (TEX86) are three well-known examples of paleothermometric proxies. These established proxies are in the realism phase of the Elderfield proxy curve (2002 Geochim. Cosmochim...
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We present a new 52 m composite record (COL17c) composed of five sedimentary sequences retrieved from the Colônia basin (Southeastern Brazil). The COL17c record is composed of two main sub-units deposited under different regimes: a peatland above ∼14 m and lacustrine sediments below. Sedimentary description and core scanning (MSCL and XRF) are firs...
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We analysed changes in mean annual air temperature (MAAT), vegetation and biomass burning on a long and continuous lake-peat sediment record from the Colônia basin, southeastern Brazil, examining the responses of a wet tropical rainforest over the last 180 ka. Stronger southern atmospheric circulation up to the latitude of Colônia was found for the...
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Radiocarbon (C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric C concentration. Although calibration curves are constructed from independently dated archives, they inva...
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Lacustrine carbonates formed in rift settings are increasingly studied not only as archives of Earth chemical and climatic history but also because they represent potential hydrocarbon source rocks and/or reservoirs. The role of magmatic gases in their formation and diagenetic evolution, hence in their reservoir properties, remains unclear. We stud...
Article
Large fluvial systems, such as the Nile River, allow a basin-scale integrated view of climatological and environmental changes. In this study, we reconstructed the Nile discharge history for the last 20 ka using molecular ratios of glycerol dialkyl glycerol tetraethers (GDGTs) and neodymium (Nd) radiogenic isotopes. By characterizing both the organ...
Article
The evolution of temperatures during the Holocene is controversial, especially for the early Holocene. The occurrence of the Holocene Thermal Maximum (HTM) during the early Holocene has recently been reconsidered and seasonal biases have been suggested in the paleoclimatic proxies. High regional variability and a low number of reliable and continuo...
Article
Subfossil trees with their annual rings constitute the most accurate and precise archive to calibrate the radiocarbon ( ¹⁴ C) method. The Holocene part of the IntCal curve is based on tree-ring chronologies, absolutely dated by dendrochronological matching. For the Northern Hemisphere, the absolute curve starts at 12,325 cal BP. For the early part...
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Cl production in the atmosphere is modulated by the magnetic field intensity of both the Sun and the Earth. The record of ³⁶Cl concentration along with that of ¹⁰Be in ice cores may therefore provide information as to their variability. To better understand the ³⁶Cl signal in glaciological archives, we measured its concentration in Talos Dome snow...
Conference Paper
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RI-OH (Ring Index of hydroxylated tetraethers) has recently been proposed to reconstruct paleotemperatures in mid-to-low latitude marginal seas. However, RI-OH has barely been tested in marginal seas under substantial terrigenous inputs. Here, we analyze tetraether lipids in two adjacent marine cores from the Gulf of Lions. We then test for the fir...
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More than 2,000 analyses of beryllium‐10 (¹⁰Be) and sulfate concentrations were performed at a nominal subannual resolution on an ice core covering the last millennium as well as on records from three sites in Antarctica (Dome C, South Pole, and Vostok) to better understand the increase in ¹⁰Be deposition during stratospheric volcanic eruptions. A...
Article
Cosmogenic in situ ¹⁴C in quartz is rapidly becoming a widely used geochronological tool for studying earth surface processes over the last 30,000 years. The Lamont-Doherty Earth Observatory houses one of the longest continuously-operating cosmogenic in situ ¹⁴C laboratories; in this contribution, we provide an update on the status of the laborator...
Article
The distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) has been shown to correlate with mean annual air temperature and is increasingly used for paleoclimate reconstructions, in particular in lakes. Numerous studies reported the occurrence of in situ production of brGDGTs in lakes. These brGDGTs are differently distributed com...
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RI‐OH (ring index of hydroxylated tetraethers) has recently been proposed to reconstruct paleotemperatures in middle‐ to low‐latitude marginal seas. However, RI‐OH has barely been tested in marginal seas under substantial terrigenous inputs. Here we analyze tetraether lipids in two adjacent marine cores from the Gulf of Lions. We then test for the...
Article
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Located in the Mediterranean Basin and close to Marseille (France), Fos-sur-Mer is situated in the vicinity of industrial harbor and agricultural lands. Its location makes it prone to mixed pollution contributions, combining the influence of residential, industrial, agricultural, maritime road and traffic sources. For this study, the origins of car...
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Radiocarbon dating archaeological bone typically requires 300–1000 mg material using standard protocols. We report the results of reducing sample size at both the pretreatment and 14C measurement stages for eight archaeological bones spanning the radiocarbon timescale at different levels of preservation. We adapted our standard collagen extraction...
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Recently, it has been confirmed that extreme solar proton events can lead to significantly increased atmospheric production rates of cosmogenic radionuclides. Evidence of such events is recorded in annually resolved natural archives, such as tree rings [carbon-14 ( ¹⁴ C)] and ice cores [beryllium-10 ( ¹⁰ Be), chlorine-36 ( ³⁶ Cl)]. Here, we show ev...
Article
The Holocene colonisation of islands by humans has invariably led to deep-seated changes in landscape dynamics and ecology. In particular, burning was a management tool commonly used by prehistoric societies and it acted as a major driver of environmental change, particularly from the Neolithic onwards. To assess the role of early human impacts (e....
Article
Carbohydrates are among the most abundant organic molecules in both aquatic and terrestrial ecosystems; however, very few studies have addressed their isotopic signature using compound-specific isotope analysis, which provides additional information on their origin (δ ¹³ C)and fate (Δ ¹⁴ C). In this study, semi-preparative liquid chromatography wit...
Article
Since the beginning of AMS, ¹⁴C analyses in foraminifera have been widely used to date deep-sea cores and to estimate reservoir ages of surface and deep ocean layers. Classical AMS requires acid hydrolysis of carbonate samples followed by graphitization of solid targets. For dating very small carbonate samples, an alternative route is to bypass the...
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Sedimentological (dry density, micro-facies analysis on thin-slides, X-ray diffraction, layer counting) and elemental analyses (X-ray fluorescence) of a 3.5-m-long sediment core (MAH-B) from saline Lake Maharlou (SW Iran) were used to infer hydrological changes over the last ~ 3800 years. The sediment consists of thin, alternating beds of evaporite...
Article
Study of the hydro-sedimentary dynamics of lakes provides key information on hydrological changes. In this work, we investigate Lake Azigza in the Moroccan Middle Atlas, a region that suffers from a scarcity of observational hydrological data necessary for a coherent management of water resources. Sedimentary deposits of Lake Azigza (32°58′N, 5°26′...
Article
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At present, Lake Chad ( ~13°0 N, ~14° E) is a shallow freshwater lake located in the Sahel/Sahara region of central northern Africa. The lake is primarily fed by the Chari-Logone river system draining a ~600 000 km2 watershed in tropical Africa. Discharge is strongly controlled by the annual passage of the intertropical convergence zone (ITCZ) and...
Article
After three years of tests and developments, the performances of the AixMICADAS facility have been established for small CO2 samples with a carbon mass inferior to 100 μg. The instrument shows very good stability and reliability when measuring small samples with its gas ion source. In this configuration, the precision is mainly limited by counting...
Conference Paper
Full-text available
In the field of paleoclimatology, it is crucial to obtain new reliable paleotemperature records. While several paleothermometers such as the UK'37 (based on alkenones) and the TEX86 (based on archaeal membrane lipids named isoprenoid tetraethers) have been used since at least a decade, several new paleothermometers like the RI-OH (ring index of hyd...
Article
Among the new proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs), the BIT index (Branched and Isoprenoid Tetraether index) is one of the most difficult to determine accurately, as shown by two round-robin GDGT studies. Sensitivity to mass spectrometer settings and tuning, and a diversity of mass spectrometry techniqu...
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After 6 years of ³⁶Cl routine operation, more than 6000 unknown samples have been measured at the 5MV French accelerator mass spectrometry (AMS) national facility ASTER (CEREGE, Aix en Provence). This paper presents the long term behavior of ASTER through the analysis of the measurements of the most used chlorine standards and reference materials,...
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The pre-industrial millennium is among the periods selected by the Paleoclimate Model Intercomparison Project (PMIP) for experiments contributing to the sixth phase of the Coupled Model Intercomparison Project (CMIP6) and the fourth phase of the PMIP (PMIP4). The past1000 transient simulations serve to investigate the response to (mainly) natural f...
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For many of archaeology’s rarest and most enigmatic bone artifacts (e.g. human remains, bone ornaments, worked bone), the destruction of the 500 mg material necessary for direct accelerator mass spectrometry (AMS) dating on graphite targets would cause irreparable damage; therefore many have not been directly dated. The recently improved gas ion so...
Article
The AixMICADAS facility is in part dedicated to research on radiocarbon ( ¹⁴ C) calibration by means of various archives. For this purpose, we are improving upon the capacity to accurately date subfossil wood. In the current study, nine chemical pretreatment protocols are tested on six wood samples of known ages. The optimization based on ¹⁴ C ages...
Conference Paper
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The Quaternary Period is characterized by the superimposition of climatic variations at the orbital (glacial and interglacial periods) and millennial (abrupt climatic events) time scales. Major fluctuations in global temperatures and ice volume occurred during this period, causing sea level changes of about 100 m at the orbital time scale. However,...
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Geochemical, sedimentological, historical and instrumental information from Melincué Lake (33°43′S/61°28′W) was analyzed in order to reconstruct main hydro-climatic changes along the Pampean region, considering the end of the Little Ice Age (LIA) and the Current Warm Period (CWP) climatic phases. Elemental X-ray fluorescence determinations were per...