Geochemical identity of pre-Dogon and Dogon populations at Bandiagara (Mali, 11th–20th cent. AD)

Bone geochemistry of pre-Dogon (11th–16th cent. AD) and Dogon (17th–20th cent. AD) populations buried in two caves of the Bandiagara Cliff (Mali) was examined for the purpose of exploring their diet and mobility. While the Dogon were the subject of extensive ethnographic studies, the lifestyle of the pre-Dogon, so-called “Tellem” is not known. We therefore compared the geochemical composition of Dogon bones with the results obtained from modern dietary surveys in Mali, to establish the parameters of a dietary model that was further applied to the pre-Dogon in order to expand our knowledge concerning their way of life. The exceptional preservation of the bones of both populations was confirmed not only at the macroscopic scale, but also at the mineralogical, histological and geochemical levels, which resemble those of fresh bones, and therefore offered ideal conditions for testing this approach. 15The application of the Bayesian mixing model FRUITS, based on bone δ13C (apatite and collagen) and bone δ N values, suggested a dietary continuity through time, from the 11th century to today. Bone barium (Ba) content revealed very restricted mobility within the Cliff while bone δ18O values indicated that Pre-Dogon and Dogon most likely occupied the Bandiagara Plateau and the Cliff, respectively

Apport de l'étude de la spéciation du manganèse dans les carbonates pélagiques à la compréhension du contrôle des séquences eustatiques du 3ème ordre

PARIS-BIUSJ-Thèses (751052125) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocSudocFranceF

Eléments de Géologie. 15 ème édition

National audienceLa Terre: une planète dans l'Univers. La dynamique de la Terre solide: géochimie et géochimie. La dynamique de la lithosphère océanique. Les constituants endogènes des enveloppes solides de la Terre: roches ignées et métamorphiques. La déformation de la lithosphère continentale. Les enveloppes fluides de la planète Terre: climats, paléoclimats,océanographie et hydrogéologie. Sédimentologie : roches et environnements sédimentaires. Notion de stratigraphie : aperçu de l'histoire de la Vie et de la Terre

What do oyster shells tell us about paleoclimatology?

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New insights into oyster high-resolution hinge growth patterns

While oyster shells are one of the most common mollusks used for the analysis of (paleo)environmental and (paleo)climatic records based on geochemical proxies, high-resolution growth rate changes still need to be determined. Promising previous works are restricted to small portions of shell sections due to difficulties in continuous growth increment revelation. Based on a mark and recapture experiment of Magallana gigas specimens reared in an intertidal area of Normandy (France) for 22 months, and a sclerochronological approach using cathodoluminescence microscopy, this study provides the longest high-resolution record of growth increments in oyster shells to date. Different growth patterns were identified likely related to the oyster age. After age 1 year, the formation of growth increments follows an expected tide-related model, leading to the mineralization of ~ 2 calcitic increments per day, together with growth rate changes at lunar and semi-lunar periodicities, and a seasonal trend with occasional growth breaks during winter when temperatures fall below ~ 6 °C. However, for oysters younger than 1 year, i.e., before reaching their sexual maturity, the growth increment analysis reveals unconventional patterns. In this case, oysters’ growth is associated with either a large number (~ 5) or less than one increment per day depending on the period. This pattern is also associated with frequent growth cessations, although the growth rate of the shell is high at this period. Our results illustrate that the high-resolution sclerochronological approach is required for accurate paleoenvironmental reconstructions based on oyster shells

What do oyster shells tell us about paleoclimatology?

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What do oyster shells tell us about paleoclimatology?

International audienc

Fluctuations of sea-water chemistry during Gargasian (Middle Aptian) time. Data from trace-element content (Mg, Sr, Mn, Fe) in hemipelagic carbonates from La Marcouline Quarry (Cassis, SE France)

In the Lower Aptian historical stratotype area (Cassis-La Bédoule, SE France), a geochemical study of the Gargasian (Middle Aptian) marl-limestone alternations of the La Marcouline quarry complements data already obtained from Bedoulian (Early Aptian) sediments there. Nannoconids are the main carbonate producers in both limestones and marls. Although diagenetic minerals, such as ankerite (2.5%) are present in small amounts, the trace-element content of bulk carbonate is very close to that of Nannoconus spp. so geochemical sequences can be defined. The long-term evolution of trace-element content was not affected by diagenetic processes, variations in carbonate mineralogy, or a change of carbonate producers. An increase of around 500 ppm in the strontium content of bulk carbonate occurs between the base of the Cabri zone (late Bedoulian) and the Algerianus zone (late Gargasian). This evolution is linked to fluctuations in seawater Sr/Ca ratios caused by variability in the influx of hydrothermal and river waters, by changes in the ratio of aragonite/calcite production and by shifts in sea level. The eustatic sequence Aptian 4, its parasequences and its key surfaces (sequence boundaries, maximum flooding surface) are clearly reflected in the evolution of the bulk-carbonate contents of manganese

What do oyster shells tell us about paleoclimatology?

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