Uranium-series measurements of the speleothem samples from the Cola cave.The concentrations of 23... more Uranium-series measurements of the speleothem samples from the Cola cave.The concentrations of 238U and 232Th were determined using the enriched 236U and 229Th isotopes, respectively. delta234Um = {[(234U/238U)sample/(234U/238U)eq] − 1} ×1000, where (234U/238U)sample is the measured atomic ratio and (234U/238U)eq is the atomic ratio at secular equilibrium.
A high-resolution bathymetric survey of the eastern half of the Gulf of Aqaba (within Saudi water... more A high-resolution bathymetric survey of the eastern half of the Gulf of Aqaba (within Saudi waters) and the Strait of Tiran was conducted on board the R/V Thuwal from May 20<sup>th</sup> to June 7<sup>th</sup>, 2018. We used a Kongsberg EM710-MK2 multibeam echo sounder (operating in the 70-100 kHz range) calibrated with CTD (Conductivity, Temperature, Depth) profiles. In order to maximize the range capability and to reduce interference from multiple returns we used a transmit fan which sequentially divides the signal into three sectors with distinct transmit frequencies and waveforms. We limited the system to a swath of 2000 m (i.e. 1000 m swath on each side of the beamer) in order to ensure appropriate beam density as to grid the data in a 10 m wide pixel raster across the track. Similarly, the survey speed was kept at 5-6 kn (~10 km/h) to limit the spacing between successive survey points and to ensure that the maximum pixel width is 10 m along the track as...
The cave of Saint-Marcel is known for its extensive network (64 km of galleries) and its history ... more The cave of Saint-Marcel is known for its extensive network (64 km of galleries) and its history of human occupation (Middle Palaeolithic and Neolithic) in the entrance area. Close observation of the main network reveals areas with high concentrations of broken speleothems, which are usually attributed to the first tourist visits of the nineteenth century. However, archaeo-geomorphological mapping of the broken speleothems, many of which are lying on the floor and sealed by stalagmite regrowth or crust, indicates intentional organisation of the underground space into speleothem supply zones and zones in which the speleothems were used to build structures. Age estimates of the stalagmite seals on these human-made structures suggest that the structures were a result of human activity that occurred between the end of the Upper Palaeolithic and the European Mesolithic. These age estimates radically change the way we look at the broken speleothems in the cave of Saint-Marcel and the structures associated with them. They bring to light the engagement of past human communities with the deep underground environment, at more than 1.5 km from the cave entrance, which can only be accessed by crossing obstacles (pits) that, today, are considered as difficult to be crossed. Our findings and ongoing research stress the unequivocal archaeological significance of the cave.
Coral Reefs and Sea-Level Change: Quaternary Records and Modelling
Malé, the capital of the Republic of Maldives, is established on an island of about 6.8 square ki... more Malé, the capital of the Republic of Maldives, is established on an island of about 6.8 square kilometres, with a maximum relief of 2.7 m and a population of 236,000 inhabitants. It is amongst the most densely populated areas on Earth and located virtually at sea-level. This study focuses on the late Pleistocene-Holocene evolution of Malé island that recently formed as part of the discontinuous North Malé Atoll rim. Understanding the formation of Malé Island is relevant in predicting its future in the context of accelerating rates of sea-level rise in the next centuries due to anthropogenic global warming. Analyses of two boreholes up to 35 m-long, published information from additional boreholes drilled on Malé Island and a high-resolution multi-beam bathymetric survey acquired along its upper slopes and deep surroundings were available for this study. Two distinct sedimentary units were recovered from the boreholes. Facies analyses of the lower unit reveal an overall deepening cora...
L'ecroulement de la Dent du Loup (Vercors nord) affecte le Senonien et localement l'Urgon... more L'ecroulement de la Dent du Loup (Vercors nord) affecte le Senonien et localement l'Urgonien. Morphologiquement, la masse ecroulee presente 3 ensembles: un replat vers 500 m, un talus dominant la plaine de l'Isere et la plaine elle-meme ou il disparait sous les alluvions recentes. Une etude morphogeologique (nature des blocs), completee par des âges sur paleosols (14C), sur concretion scellant l'ecroulement (U/Th) et sur la niche d'arrachement (36Cl) a permis de distinguer 3 evenements anciens et un ensemble d'evenements recents. Les 3 evenements anciens dates se situent autour de 18 ka, entre 11 et 10 ka et vers 8 ka, les 2 premiers evenements affectant le Senonien alors que le 3eme n'affecte que l'Urgonien (niche bien visible dans le versant). Tous ces evenements ont atteint la plaine. Un dernier ensemble, correspondant a des unites seulement presentes sur le replat, est associe a des coulees de boue, alimentees par des resurgences temporaires du ka...
. A multi-method approach aimed at characterizing carbonate parietal deposits and at proposing a ... more . A multi-method approach aimed at characterizing carbonate parietal deposits and at proposing a chronology for these carbonate crusts is described. Dating was performed by radiometric methods (C-14 for recent samples, and U-series) on samples that had been characterized beforehand using optical and cathodoluminescence microscopy, and Fourier Transform Infrared microspectroscopy. For U-series, high precision on U-Th ages was achieved using liquid phase multicollector-ICP-MS applied to large samples, while laser-ablation single collector - ICP-SFMS provided information on the reliability of the sampling with a high spatial resolution. This methodology, based on the combination of these two techniques reinforced by the information obtained by the calcite characterization methods, was applied to carbonate deposits from the cave of the Trou du Renard (Soyons, France). The ages obtained with the two U-Th dating techniques are comparable and illustrate that different laminae were deposited at different rates in the samples. In the future, this procedure based on the mineralogical and geochemical characterization of the samples and their dating by radiometric methods will be applied to the layers of parietal carbonates deposited on Palaeolithic decorated walls. When the crystallization is slow, the U/Th dating method by imaging technique is of interest as well as that by multicollector-ICP-MS in liquid phase. The development of robust dating methods on very small quantities of material will make it possible to define the chronological framework of cave rock art.
Coral Reefs and Sea-Level Change: Quaternary Records and Modelling
The partial melting of Earth’s bi-polar ice sheets since the Last Glacial Maximum (LGM) has trans... more The partial melting of Earth’s bi-polar ice sheets since the Last Glacial Maximum (LGM) has translated into a ~ 120 m amplitude stepwise sea-level rise punctuated by three major meltwater pulses that were tracked and recorded with some of the best accuracy by coral reefs. However, the initial meltwater pulse marking the end of the LGM, at 19 ka, is anchored in only two palaeo reefs (Barbados, Great Barrier Reef). Here, the authors present the analysis of a coralgal reef that thrived along the south-east Papua New Guinea Peninsula outer shelf during this initial pulse. In the cone of a piston core, a shallow Goniastrea retiformis coral colony was retrieved at 111 m below present sea-level and uranium/thorium dated to 19.4 ka BP. This colony had been buried beneath the debris of a proximal coralgal reef before its partial drowning at 14.5 ka BP. Seismic survey data suggest that the reef edifice was established directly on the eroded top of a lowstand shelf-edge delta, partially drowne...
Uranium-series measurements of the speleothem samples from the Cola cave.The concentrations of 23... more Uranium-series measurements of the speleothem samples from the Cola cave.The concentrations of 238U and 232Th were determined using the enriched 236U and 229Th isotopes, respectively. delta234Um = {[(234U/238U)sample/(234U/238U)eq] − 1} ×1000, where (234U/238U)sample is the measured atomic ratio and (234U/238U)eq is the atomic ratio at secular equilibrium.
A high-resolution bathymetric survey of the eastern half of the Gulf of Aqaba (within Saudi water... more A high-resolution bathymetric survey of the eastern half of the Gulf of Aqaba (within Saudi waters) and the Strait of Tiran was conducted on board the R/V Thuwal from May 20<sup>th</sup> to June 7<sup>th</sup>, 2018. We used a Kongsberg EM710-MK2 multibeam echo sounder (operating in the 70-100 kHz range) calibrated with CTD (Conductivity, Temperature, Depth) profiles. In order to maximize the range capability and to reduce interference from multiple returns we used a transmit fan which sequentially divides the signal into three sectors with distinct transmit frequencies and waveforms. We limited the system to a swath of 2000 m (i.e. 1000 m swath on each side of the beamer) in order to ensure appropriate beam density as to grid the data in a 10 m wide pixel raster across the track. Similarly, the survey speed was kept at 5-6 kn (~10 km/h) to limit the spacing between successive survey points and to ensure that the maximum pixel width is 10 m along the track as...
The cave of Saint-Marcel is known for its extensive network (64 km of galleries) and its history ... more The cave of Saint-Marcel is known for its extensive network (64 km of galleries) and its history of human occupation (Middle Palaeolithic and Neolithic) in the entrance area. Close observation of the main network reveals areas with high concentrations of broken speleothems, which are usually attributed to the first tourist visits of the nineteenth century. However, archaeo-geomorphological mapping of the broken speleothems, many of which are lying on the floor and sealed by stalagmite regrowth or crust, indicates intentional organisation of the underground space into speleothem supply zones and zones in which the speleothems were used to build structures. Age estimates of the stalagmite seals on these human-made structures suggest that the structures were a result of human activity that occurred between the end of the Upper Palaeolithic and the European Mesolithic. These age estimates radically change the way we look at the broken speleothems in the cave of Saint-Marcel and the structures associated with them. They bring to light the engagement of past human communities with the deep underground environment, at more than 1.5 km from the cave entrance, which can only be accessed by crossing obstacles (pits) that, today, are considered as difficult to be crossed. Our findings and ongoing research stress the unequivocal archaeological significance of the cave.
Coral Reefs and Sea-Level Change: Quaternary Records and Modelling
Malé, the capital of the Republic of Maldives, is established on an island of about 6.8 square ki... more Malé, the capital of the Republic of Maldives, is established on an island of about 6.8 square kilometres, with a maximum relief of 2.7 m and a population of 236,000 inhabitants. It is amongst the most densely populated areas on Earth and located virtually at sea-level. This study focuses on the late Pleistocene-Holocene evolution of Malé island that recently formed as part of the discontinuous North Malé Atoll rim. Understanding the formation of Malé Island is relevant in predicting its future in the context of accelerating rates of sea-level rise in the next centuries due to anthropogenic global warming. Analyses of two boreholes up to 35 m-long, published information from additional boreholes drilled on Malé Island and a high-resolution multi-beam bathymetric survey acquired along its upper slopes and deep surroundings were available for this study. Two distinct sedimentary units were recovered from the boreholes. Facies analyses of the lower unit reveal an overall deepening cora...
L'ecroulement de la Dent du Loup (Vercors nord) affecte le Senonien et localement l'Urgon... more L'ecroulement de la Dent du Loup (Vercors nord) affecte le Senonien et localement l'Urgonien. Morphologiquement, la masse ecroulee presente 3 ensembles: un replat vers 500 m, un talus dominant la plaine de l'Isere et la plaine elle-meme ou il disparait sous les alluvions recentes. Une etude morphogeologique (nature des blocs), completee par des âges sur paleosols (14C), sur concretion scellant l'ecroulement (U/Th) et sur la niche d'arrachement (36Cl) a permis de distinguer 3 evenements anciens et un ensemble d'evenements recents. Les 3 evenements anciens dates se situent autour de 18 ka, entre 11 et 10 ka et vers 8 ka, les 2 premiers evenements affectant le Senonien alors que le 3eme n'affecte que l'Urgonien (niche bien visible dans le versant). Tous ces evenements ont atteint la plaine. Un dernier ensemble, correspondant a des unites seulement presentes sur le replat, est associe a des coulees de boue, alimentees par des resurgences temporaires du ka...
. A multi-method approach aimed at characterizing carbonate parietal deposits and at proposing a ... more . A multi-method approach aimed at characterizing carbonate parietal deposits and at proposing a chronology for these carbonate crusts is described. Dating was performed by radiometric methods (C-14 for recent samples, and U-series) on samples that had been characterized beforehand using optical and cathodoluminescence microscopy, and Fourier Transform Infrared microspectroscopy. For U-series, high precision on U-Th ages was achieved using liquid phase multicollector-ICP-MS applied to large samples, while laser-ablation single collector - ICP-SFMS provided information on the reliability of the sampling with a high spatial resolution. This methodology, based on the combination of these two techniques reinforced by the information obtained by the calcite characterization methods, was applied to carbonate deposits from the cave of the Trou du Renard (Soyons, France). The ages obtained with the two U-Th dating techniques are comparable and illustrate that different laminae were deposited at different rates in the samples. In the future, this procedure based on the mineralogical and geochemical characterization of the samples and their dating by radiometric methods will be applied to the layers of parietal carbonates deposited on Palaeolithic decorated walls. When the crystallization is slow, the U/Th dating method by imaging technique is of interest as well as that by multicollector-ICP-MS in liquid phase. The development of robust dating methods on very small quantities of material will make it possible to define the chronological framework of cave rock art.
Coral Reefs and Sea-Level Change: Quaternary Records and Modelling
The partial melting of Earth’s bi-polar ice sheets since the Last Glacial Maximum (LGM) has trans... more The partial melting of Earth’s bi-polar ice sheets since the Last Glacial Maximum (LGM) has translated into a ~ 120 m amplitude stepwise sea-level rise punctuated by three major meltwater pulses that were tracked and recorded with some of the best accuracy by coral reefs. However, the initial meltwater pulse marking the end of the LGM, at 19 ka, is anchored in only two palaeo reefs (Barbados, Great Barrier Reef). Here, the authors present the analysis of a coralgal reef that thrived along the south-east Papua New Guinea Peninsula outer shelf during this initial pulse. In the cone of a piston core, a shallow Goniastrea retiformis coral colony was retrieved at 111 m below present sea-level and uranium/thorium dated to 19.4 ka BP. This colony had been buried beneath the debris of a proximal coralgal reef before its partial drowning at 14.5 ka BP. Seismic survey data suggest that the reef edifice was established directly on the eroded top of a lowstand shelf-edge delta, partially drowne...
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