Sedimentary Records in the Lesser Antilles Fore‐Arc Basins Provide Evidence of Large Late Quaternary Megathrust Earthquakes
Abstract The seismic potential of the Lesser Antilles subduction zone is poorly known and highly debated. Only two damaging earthquakes have been reported in the historical period, in 1839 and 1843, but their sources and magnitude are still uncertain. Global Navigation Satellite Systems and coral data contradict each other, and no conclusion has been reached on the coupling ratio of the plate interface. Given the threat posed by the possible occurrence of a large megathrust earthquake, it is crucial to gain information on prehistorical events. We present the results of a submarine paleoseismological study that covers an exceptional ∼120 Kyr‐long period. We studied the sediments sampled in six up to 26 m‐long piston cores collected in deep fore‐arc basins located over the epicentral region of the 1843 earthquake. Using a multiproxy approach combining geophysical, geochemical, and sedimentological analysis, biostratigraphy and radiocarbon dating, we identified, characterized, and dated numerous event deposits that we then correlated with the sampled basins over an up to 160 km‐long area. We show that at least 33 earthquakes likely triggered these sediment remobilizations in the last 120 Kyr. Four of these events promoted exceptional deposits of turbidites + homogenites. From peak ground acceleration calculated for potential earthquakes occurring on various faults, and the absence of deposits linked to the historical earthquakes, we propose that the sources are likely megathrust earthquakes. Over the last 60 Kyr, we inferred at least three 15–25 Kyr‐long seismic cycles in which the recurrence times of earthquakes shortens from ∼5 to ∼2 Kyr.
(Geochemistry, Geophysics, Geosystems. vol. 25, 31/01/2024)
IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, LDEO, GEOAZUR 7329, INSU - CNRS, UniCA, CNRS, IRD [Occitanie], UniCA, ISTerre, IRD, INSU - CNRS, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, UGA, GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS, UBO EPE, MNHN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEOAS, OSU, LOCEAN-VOG, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, ISMER, UQAR, iSTeP, INSU - CNRS, SU, CNRS, RDT, IFREMER, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France]
Response of vegetative and reproductive organs of Cucurbita pepo L. Subsp pepo ‘Allegria’ exposed to aged dieldrin contamination in regards to soil concentration and plant development
Aims Dieldrin is an Organochlorine Pesticides (OCPs) which, due to its persistence in agricultural soils, continues to be a source of contamination for crops, especially Cucurbita pepo L. subsp pepo ( C. pepo L.). The latter are able to absorb dieldrin from contaminated soils and transfer it from the roots to the shoots. However, dieldrin allocation has been partially studied, especially in the shoots. This study aims at characterizing dieldrin distribution in the different plant organs according to soil contamination and plant growth. Methods This was achieved by growing C. pepo L. ‘Allegria’ in soil mixtures presenting 5 levels of dieldrin concentration (< 1 to 145 µg kg −1 ) and by harvesting them after different exposure periods (30, 90 and 140 d after transplant). Results The results showed (i) the predominance of the root impregnation path, (ii) that dieldrin concentration in the vegetative organs of C. pepo L. ‘Allegria’ increased with soil concentration while (iii) it stabilized for reproductive organs at soil concentrations exceeding 50 µg kg −1 DW. The bioconcentration factors (BCFs) for vegetative organs were classified as follows: stems (70) > roots (47) > leaves (19). Furthermore, the mass distribution of dieldrin was more dependent on variations in organ mass fraction with plant development than variations of dieldrin concentration in the different organs. Conclusions These results are of main importance for (i) the identification of dieldrin contaminated agricultural plots using phytoscreening methods as well as for (ii) their phytomanagement providing crucial allocation information for phytoextraction purposes.
(Plant and Soil. vol. 499, n° 0032-079X, pp. 655 - 669, 23/01/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BioGeCo, UB, INRAE
Copper Speciation in Wine Growing-Drain Waters: Mobilization, Transport, and Environmental Diffusion
Copper (Cu) has been used to treat vines for a long time, which has led to its accumulation in vineyard soils. In the present work, the mobilization of copper from these soils and its transport, and diffusion outside the plots by drain water were investigated. For this, the distribution of copper between the dissolved and colloidal phases, and within the colloidal phase, of these waters was determined using an investigation strategy based on the coupling between a size separation technique, asymmetric flow field-flow fractionation, and several detectors. First, the total copper concentrations in water from different drains were monitored over a period of 2 years: Cu was mainly found in the fraction of < 450 nm. Then, the distribution of copper on the size continuum was more closely studied in water from one of the drains, sampled over a winter period. Between 45 and 75% of Cu was found in the 2–450 nm colloidal fraction. The <450 nm colloidal phase of the drain waters was found to be mainly composed of humic acids (~15 to 60 mg L−1) and clay-rich particles (~100 to 650 mg (Al) L−1). These particles also contained (hydr)oxides of iron and manganese. The concentrations of Fe and Mn were approximately 100 to 200 times lower than those of Al. The majority of humic acids had an apparent molar mass of ≤ 10 kDa. They were distributed along the size continuum: (i) in a population with an average size of ~20 nm, probably consisting of supramolecular entities, and (ii) associated with clay-rich particles with a size of ~120–200 nm. Copper was found to be complexed with humic acids and associated with clays via clay-humic complexes. Copper mobilization from the soil to the water and its transport to the drain water appeared governed by the soil humidity level and the rainfall.
(Environments. vol. 11, n° 2076-3298, pp. 19, 19/01/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPREM, UPPA, INC-CNRS, CNRS
Secular shoreline response to large-scale estuarine shoal migration and welding
The 14.5-km North-Médoc coast, southwest France, is a high-energy mesoto macro-tidal environment adjacent to the largest estuary in Europe. Over the last centuries, this coastline has locally suffered periods of severe erosion, threatening coastal infrastructures and requiring the progressive implementation of coastal structures and, more recently, localized beach nourishments. This contribution combines 84 years (1937-2021) of shoreline data from various sources, 118 years (1903-2021) of shallow water bathymetric surveys and historical photographs. Results show that, averaged in both time and space, the coast eroded by-0.6 m/yr over the last 84 years, but with a large alongshore and temporal variability. Erosion is locally peaking at-5.2 m/yr, while accretion is restricted to a remote 2.5-km and locally peaks at 5.4 m/yr. A salient characteristic of shoreline evolution is the alternation of rapid erosion (<-5 m/yr) and dramatic accretion (> 20 m/yr) periods over relatively short intervals (≈ 10 years) and across limited alongshore distances (e.g. couple of
(Geomorphology. vol. 445, n° 0169-555X, pp. 108972, 15/01/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM
Hot carbonates deep within the Chicxulub impact structure
Abstract Constraining the thermodynamic conditions within an impact structure during and after hypervelocity impacts is extremely challenging due to the transient thermal regimes. This work uses carbonate clumped-isotope thermometry to reconstruct absolute temperatures of impact lithologies within and close to the ∼66 Myr old Chicxulub crater (Yucatán, México). We present stable oxygen (δ18O), carbon (δ13C), and clumped-isotope (Δ47) data for carbonate-bearing impact breccias, impact melt rock, and target lithologies from four drill cores on a transect through the Chicxulub structure from the northern peak ring to the southern proximal ejecta blanket. Clumped isotope-derived temperatures (T(Δ47)) are consistently higher than maximum Late Cretaceous sea surface temperatures (35.5°C), except in the case of Paleogene limestones and melt-poor impact breccias outside of the crater, confirming the influence of burial diagenesis and a widespread and long-lived hydrothermal system. The melt-poor breccia unit outside the crater is overlain by melt-rich impact breccia yielding a much higher T(Δ47) of 111 ± 10°C (1 standard error [SE]), which likely traces the thermal processing of carbonate material during ejection. Finally, T(Δ47) up to 327 ± 33°C (1 SE) is determined for the lower suevite and impact melt rock intervals within the crater. The highest temperatures are related to distinct petrological features associated with decarbonation and rapid back-reaction, in which highly reactive CaO recombines with impact-released CO2 to form secondary CaCO3 phases. These observations have important climatic implications for the Cretaceous–Paleogene mass extinction event, as current numerical models likely overestimate the release of CO2 from the Chicxulub impact event.
(PNAS Nexus. vol. 3, n° 2752-6542, 11/01/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Co-infection of two eukaryotic pathogens within clam populations in Arcachon Bay
The parasitic species Perkinsus olseni (= atlanticus ) (Perkinsea, Alveolata) infects a wide range of mollusc species and is responsible for mortality events and economic losses in the aquaculture industry and fisheries worldwide. Thus far, most studies conducted in this field have approached the problem from a “one parasite-one disease” perspective, notably with regards to commercially relevant clam species, while the impact of other Perkinsus species should also be considered as it could play a key role in the disease phenotype and dynamics. Co-infection of P. olseni and P. chesapeaki has already been sporadically described in Manila clam populations in Europe. Here, we describe for the first time the parasitic distribution of two Perkinsus species, P. olseni and P. chesapeaki , in individual clam organs and in five different locations across Arcachon Bay (France), using simultaneous in situ detection by quantitative PCR (qPCR) duplex methodology. We show that P. olseni single-infection largely dominated prevalence (46–84%) with high intensities of infection (7.2 to 8.5 log-nb of copies. g −1 of wet tissue of Manila clam) depending on location, suggesting that infection is driven by the abiotic characteristics of stations and physiological states of the host. Conversely, single P. chesapeaki infections were observed in only two sampling stations, Ile aux Oiseaux and Gujan, with low prevalences 2 and 14%, respectively. Interestingly, the co-infection by both Perkinsus spp., ranging in prevalence from 12 to 34%, was distributed across four stations of Arcachon Bay, and was detected in one or two organs maximum. Within these co-infected organs, P. olseni largely dominated the global parasitic load. Hence, the co-infection dynamics between P. olseni and P. chesapeaki may rely on a facilitating role of P. olseni in developing a primary infection which in turn may help P. chesapeaki infect R. philippinarum as a reservoir for a preferred host. This ecological study demonstrates that the detection and quantification of both parasitic species, P. olseni and P. chesapeaki , is essential and timely in resolving cryptic infections and their consequences on individual hosts and clam populations.
(Frontiers in Microbiology. vol. 14, n° 1664-302X, pp. 1250947, 08/01/2024)
LEMAR, IRD, IFREMER, UBO EPE, CNRS, CRIOBE, UPVD, EPHE, PSL, CNRS, SBR, SU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ASIM, IFREMER
Remotely sensing potential climate change tipping points across scales
AbstractPotential climate tipping points pose a growing risk for societies, and policy is calling for improved anticipation of them. Satellite remote sensing can play a unique role in identifying and anticipating tipping phenomena across scales. Where satellite records are too short for temporal early warning of tipping points, complementary spatial indicators can leverage the exceptional spatial-temporal coverage of remotely sensed data to detect changing resilience of vulnerable systems. Combining Earth observation with Earth system models can improve process-based understanding of tipping points, their interactions, and potential tipping cascades. Such fine-resolution sensing can support climate tipping point risk management across scales.
(Nature Communications. vol. 15, n° 2041-1723, 06/01/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Offshore evidence of historic and prehistoric tsunamis on the north shore of Tutuila (American Samoa)
Although research dealing with the geological evidence of past tsunamis has increased significantly in the last two decades, studies of tsunami deposits emplaced during the backwash phases are still underrepresented. Here, we provide the first investigation of tsunami backwash deposits all around an island (Tutuila Island, American Samoa), in the southwest of the Pacific Ring of Fire. We decipher the sedimentary record preserved offshore an open bay (Fagafue) and within a sheltered bay (Masefau) on the north shore of Tutuila. Backwash deposits of three historic tsunamis, namely the 2009 South Pacific, 1960 Valdivia and 1917 Tonga Trench tsunamis, were identified in sediment cores, based on sedimentological, geochemical and chronological data. Deposits were characterized by a geochemical terrestrial signature (Ti/Ca and K), while the grain size characteristics differed, being finer offshore the open bay and coarser within the sheltered bay. The 2009 South Pacific and the 1960 Valdivia tsunamis are recorded on both the north (Masefau and off Fagafue bays) and south (Pago Pago Bay) shores of Tutuila, providing the first correlation of tsunami backwash deposits all around an island. Furthermore, the present study presents the first geological evidence of backwash associated with a large 15-16th century tsunami, which also affected many parts of the South Pacific, as well as that of an older event between the 11th and 14th century. Studies of tsunami backwash deposits provide means to extend the geological record of these high energy events, due to the generally good preservation potential of the deposits.
(Sedimentary Geology, n° 0037-0738, pp. 106572, 05/01/2024)
LIENSs, INSU - CNRS, ULR, CNRS, BEES, UNSW, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Imaging hydrological dynamics in karst unsaturated zones by time-lapse electrical resistivity tomography
The hydrodynamics of karst terrain are highly complex due to the diverse fractures and reservoirs within limestone formations. The time delay between rainfall events and subsequent flow into reservoirs exhibits significant variability. However, these hydrological processes are not easily visualized in karst topography. Subsurface geophysics, specifically 2D time-lapse electrical resistivity tomography (ERT), provides an effective method for studying the relationships between hydrological and geophysical features. In our research, we adopted ERT in the Karst Critical Zone (KCZ) to visualize specific karstic zones, including cave galleries, water storage reservoirs, wetting fronts, soil layers, and potential preferential flow paths down to a depth of 20 m. To capture spatial and seasonal variations in resistivity, we presented a comprehensive approach by combining sixteen inversion models obtained between February 2020 and September 2022 above the Villars Cave in SW-France-a well-known prehistoric cave. We used a multi-dimensional statistical technique called Hierarchical Agglomerative Clustering (HAC) to create a composite model that divided the synthetic ERT image into eight clusters representing different karst critical zones. The ERT image clearly visualized the cave gallery with high resistivity values that remained consistent throughout the seasons. Our analysis revealed a close seasonal relationship between water excess and resistivity variations in most infiltration zones, with time delays increasing with depth. The karst reservoirs, located at significant depths compared to other clusters, displayed sensitivity to changes in water excess but were primarily affected by fluctuations in water conductivity, particularly during summer or dry periods. These findings have significant implications for predicting rainwater infiltration pathways into caves, thereby assisting in the conservation and preservation of prehistoric caves and their cultural heritage.
(Science of the Total Environment. vol. 907, n° 0048-9697, pp. 168037, 01/01/2024)
I2M-BX, UB, CNRS, INRAE, UB, UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Temperature and hydrological variations during the late-glacial in the Central Mediterranean: Application of the novel ostracod-clumped isotope thermometer
This study shows, for the first time, the absence of a vital effect in the clumped isotope carbonate (Δ47) fossil ostracod signal and confirms the ability of the novel ostracod-Δ47 thermometer to reconstruct past temperatures and hydrological conditions in complex lacustrine systems. Furthermore, the application of Δ47 analyses on the ostracod species Candona angulata and Cyprideis torosa from Lake Trasimeno record (central Italy), which today precipitate their shells during the cold and the warm season respectively provides evidence that by combining biological (i.e., ostracod shell precipitation timing), paleontological (i.e., identification of ostracod species) and geochemical (i.e., Δ47) approaches, the ostracod-Δ47 thermometer accurately reconstructs past seasonality. Despite the absence of a vital effect, not all species can be combined for Δ47 analyses in environments with seasonal temperature variations; only those that precipitate their shells during the same season should be considered. The application of the ostracod-Δ47 thermometer on the Trasimeno lacustrine record gives rise to the first continental warm season paleotemperature reconstruction of the last 43 ky in central Mediterranean area. The combination of Δ47 and oxygen isotope composition (δ18Oost) measured on ostracod shells provides the isotopic composition of the water from which the carbonate precipitated (δ18Ow) and thereby, changes in the evaporation/precipitation balance in this area. Before the Last Glacial Maximum (LGM), equivalent to the Marine Isotopic Stage 3 (MIS3, from 43 to 29ky), warm season temperatures ranged from 15 ± 1.6 °C to 22 ± 2.3 °C, equivalent to 2 to 6 °C colder than today. Hydrological conditions during this period are similar to the present-day ones, characterized by a permanent lake and a high evaporation/precipitation ratio (E/P). The drastic decrease of the warm season temperatures (ranging from 10 ± 2.9 °C to 17 ± 3.1 °C) and of the E/P ratio during LGM and Late-glacial (MIS2, from 29 to 11.6 ky) correspond to the global climate cooling and low summer insolation, suggesting an amplifying role, of the latter, in the effects of the millennial scale climatic variations. At the Pleistocene/Holocene transition, both warm season temperature (25 ± 2 °C) and the E/P ratio increased in conjunction with the summer insolation. During the early Holocene, warm season temperature (23 ± 2 °C) closely resembles present-day values. However, cold season temperature (12 ± 2 °C) is approximately 4 °CC warmer than today. Notably, no hydrological differences are identified between the warm and the cold season underlying a lower seasonality contrast compared to the present, along with enhanced warm season precipitation. The good agreement between the Δ47 temperatures reconstructed for the last 1 ky and the temperatures presently recorded at Lake Trasimeno (8 °C cold and 22 °C for warm season), confirms the accuracy of the analyses and the applicability of the ostracod-Δ47 thermometer to reconstruct seasonal temperature changes.
(Earth and Planetary Science Letters. vol. 625, n° 0012-821X, pp. 118470, 01/01/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS