Deglaciation and volcano-seismic activity in Northern Iceland : Holocene and Early Eemian
(Geodinamica Acta. vol. 18 (1), n° 0985-3111, pp. 81-100, 25/08/2026)
PBDS, INSU - CNRS, CNRS, LPGN, UN, CNRS, GR, UR, INSU - CNRS, CNRS, MNHN, UPMC, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
A slab-on-slab model for the Flims rockslide (Swiss Alps)
(Canadian Geotechnical Journal, n° 0008-3674, pp. 587-600, 25/08/2026)
GEOSCIENCES, PSL, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UP1, LGP, UP1, UPEC UP12, CNRS
The biogeography of major diatom taxa in Southern Ocean sediments
Diatoms from 228 Southern Ocean core-top sediment samples were examined to determine the geographic distributions of 32 major diatom species/taxa preserved in the sediments of three zonally-distinct regions; Sea Ice, Open Ocean and the Tropical/Subtropical. In the first of three papers, 14 species/taxa occurring in the region where sea ice covers the ocean surface on an annual basis are geographically documented. Comparisons are drawn between the diatom abundances on the sea floor, sea ice parameters (annual duration and concentration in February and September) and February sea-surface temperature. Such parameters are commonly used in reconstructing past oceanographic conditions in the Sea Ice and Open Ocean zones. Analysis of the geographic patterns and sea-surface parameter correlations reveals species-specific distributions regulated primarily by sea ice coverage and sea-surface temperature, which support the use of diatom remains for the estimation of these past sea-surface environmental parameters. Comparison with reliable accounts of the 14 species from the sediments or plankton also provides the first glimpses into species-specific ecology and habitat linkages.
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 223, n° 0031-0182, pp. 93-126, 25/08/2026)
UTAS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Live foraminiferal faunas from a 2800 m deep lower canyon station from the Bay of Biscay : Faunal response to focusing of refractory organic matter
(Deep Sea Research. vol. 52, n° 0146-6291, pp. 1189-1227, 25/08/2026)
UA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOBB, OOB, UPMC, CNRS, UPMC, INSU - CNRS, CNRS
Live foraminiferal faunas from a 2800 m deep lower canyon station from the Bay of Biscay: Faunal response to focusing of refractory organic matter
A 2800 m deep station was sampled on three occasions, in January 1999, June 1999 and April 2000, in the lower part of Cap-Ferret Canyon (Bay of Biscay). This area is characterised by a rapid accumulation of fine-grained sediments and by important inputs of reworked organic matter in an intermediate state of decay. Diagenetic reactions within the sediment follow the well-established depth sequence resulting from the oxidation of organic deposits by different electron acceptors. At our station, live benthic foraminiferal faunas differ strongly from faunas previously collected at nearby open slope sites at a comparable water depth. Spectacularly high densities of deep infaunal species are observed in the deeper parts of the sediment for all three sampling periods. In our opinion, these high deep infaunal densities are a direct response to the massive flux of partially degraded organic matter, which is slowly introduced into the deeper parts of the sediment, where it induces a rather stable succession of redox gradients. Melonis barleeanus lives in the dysoxic part of the sediment whereas Globobulimina affinis appears preferentially close to the zero oxygen boundary. Both taxa occupy niches where the highest content of Mn (III, IV)-oxides and -oxihydroxides and Fe (III)-oxides are recorded. The fact that most of the geochemical reactions within the sediment are directly or indirectly catalysed by heterotrophic and chemolithoautotrophic bacterial consortia could suggest that deep infaunal foraminifera may be highly specialised protozoans able to feed on, or live in symbiosis with these prokaryotic communities.
(Deep Sea Research Part I: Oceanographic Research Papers. vol. 52, n° 0967-0637, pp. 1189-1227, 25/08/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOMIC, OOB, UPMC, CNRS, UPMC, CNRS
Evidence of a major environmental change recorded in a macrotidal bay (Marennes-Oléron Bay, France) by correlation between VHR seismic profiles and cores
New, very high-resolution (25 cm) seismic profiles have revealed the internal architecture of the infilling of a macrotidal bay, the Marennes-Oléron Bay, France. Within this geometry, a major seismic unconformity has been correlated with core data. This correlation provides evidence that the seismic unconformity corresponds to a sharp grain-size decrease. Both seismic and core data indicate that this change of grain size can be interpreted as a record of a recent (around 1,000 years b.p.) decrease in hydrodynamical energy with time and/or a larger supply of fine-grained material. This recent environmental change can be related to natural infilling of the Marennes Oléron Bay, and to tidal prism decrease, increasing human activities (e.g. land reclamation, deforestation, agricultural land use) and climate fluctuations during the late Holocene, such as the transition between the cold period of the Dark Ages (1,550–1,050 years b.p.) and the Medieval warm period (1,050–550 years b.p.).
(Geomarine letters. vol. 1, pp. 1-10, 25/08/2026)
M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, CLDG, ULR, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Paleoseismic inferences from a high-resolution marine sedimentary record in northern Chile (23°S) .
The active margin of northern Chile is characterized by strong seismic events which induce gravity instability for sedimentary sequences located along the outer forearc of the Andean range. Even though the narrow continental platform of this area limits the accumulation of marine sediments, a detailed paleoceanographic reconstruction, using high-resolution sedimentological and geochronological techniques, of a Holocene sedimentary sequence in Mejillones bay (23°S) provides important tools to infer the occurrence of past great subduction earthquakes and/or associated tsunamis. From the analyses of short cores retrieved in this shallow marine basin, we infer the occurrence of two strong seismic events during historical times. The first one, dated between the years 1409 and 1449 AD, produced an angular unconformity and associated lenticular coarse-grained deposits generated after local reworking of shallower material. The second one, dated between the years 1754 and 1789 AD, caused slumping, erosive processes and local reworking of material. The analysis of seismic profile data acquired in this bay allowed the recognition of a major slump deposit within the upper sedimentary sequence, tentatively dated as of Middle Holocene age. This event might record the greatest earthquake (and tsunami) affecting the basin within the last few thousand years. We interpret that destabilization of sediments occurs most probably in response to local reactivation of faults within the Mejillones peninsula during strong earthquakes, especially the Mejillones fault.
(Tectonophysics. vol. 399, n° 0040-1951, pp. 381-398, 25/08/2026)
FCFM, UCHILE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, PALEOTROPIQUE, ISTO, INSU - CNRS, UO, CNRS, SERNAGEOMIN
Axial incision: The key to understand submarine canyon evolution (in the western Gulf of Lion)
A detailed morphological analysis of the outer shelf and continental slope of the Western Gulf of Lion is presented, based on swath bathymetry data together with sub-bottom profiles and high resolution seismic reflection profiles. These data reveal two main erosive features, of very different dimensions: the axial incision and the canyon's major valley. The height of axial incisions' flanks with respect to the canyon deepest point (the thalweg) ranges from 40 to 150 m. It creates a small axial erosive path within the canyon's major valley, which is typically bounded by flanks of more than 700 m in height. We interpret the axial incision observed in the sea floor as the imprint of turbidity currents that eroded the floor of canyons during phases of connection to rivers (hyperpycnal turbidity current). Such currents are most likely to have formed during the Last Glacial Maximum (LGM) as both proximity of the shoreline (due to the lowstand of sea level) and high detrital sediment supply (due to glacial abrasion upstream) increased the flow of sediments delivered to the canyon heads. Fossil axial incisions, observed in seismic lines, are related to equivalent conditions. The axial incision, however, has a key influence on canyon evolution as it triggers mass wasting of different sizes that affect the canyon's major valley (head and flanks). We interpret the geometry of the canyon's major valley as the result of recurrent activity of axial incisions. These periods of activity occurred during low sea levels at glacial maxima and show a cyclicity of 100,000 years for the last 400,000 years.
(Marine and Petroleum Geology. vol. 22 (6-7), n° 0264-8172, pp. 805-826, 25/08/2026)
LDO, INSU - CNRS, UBO EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Variabilité spatiale de la sédimentation organique dans les SYSTEMES CHENAL/LEVEES DE L'éventail détritique profond DU ZAÏRE
Si les processus qui contrôlent la distribution de la matière organique terrestre dans les deltas sont relativement bien connus, la dispersion de la matière organique terrigène vers l'offshore profond et l'impact des variations climatiques et eustatiques sur la sédimentation organique terrigène dans les cônes sous-marins profonds font partie des grandes questions qui méritent d'être examinées, tant du point de vue académique –impact sur le cycle du carbone– qu'industriel –nature et distribution des roches-mères pétrolières–. C'est pourquoi nous étudions le cône sous-marin profond du Zaïre dans le cadre du GDR Marges Continentales. Le système chenal-levée turbiditique actuellement actif de ce deep sea fan se caractérise par un réseau très sinueux et fortement incisé. Le chenal turbiditique est essentiellement une zone de transit où ne sont préservées que les parties les plus grossières des écoulements turbiditiques. Les levées, au contraire, enregistrent les débordements des écoulements turbiditiques qui passent successivement dans le chenal. Dans la partie amont les débordements sont réduits et se produisent préférentiellement dans la partie distale du système où l'encaissement des chenaux est moindre. Ainsi, les taux d'accumulation sur les levées sont plus importants d'un facteur 10 dans la partie distale du système. La variabilité spatiale, tant longitudinale que transversale, des enrichissements en matière organique est analysée le long de deux transects chenal-levées afin de déterminer si tels ou tels fragments organiques se trouvent préférentiellement accumulés en fonction de leur taille, de leur densité ou de leur forme. La richesse en carbone organique et le type de particules organiques sont déterminés par une combinaison d'études sédimentologiques, géochimiques globales (pyrolyse Rock-Eval, isotopie de N et C) et palynologiques. Un échantillonnage à très haute résolution (1 à 2 cm) a été pratiqué dans quelques successions turbiditiques, afin d'estimer la variabilité temporelle à l'échelle d'un événement turbiditique ou d'une succession de 2 à 3 événements turbiditiques. Les argilites et siltites fines qui constituent les dépôts de levée sont pratiquement dépourvues de carbonate (< 4%) mais contiennent une fraction notable de matière organique (3 % de Carbone Organique Total en moyenne). Sur le transect amont, les argilites déposées au plus près du chenal sont un peu plus riches en carbone organique que celles déposées plus loin du chenal avec une moyenne de 3,09 % contre 2,57 % COT. On constate sur les deux transects que la qualité de la matière organique est systématiquement meilleure dans les faciès plus éloignés du chenal par rapport à ceux des carottes plus proximales. Dans les faciès distaux, les valeurs de l'index d'hydrogène sont un peu plus fortes (ΔIH = 40) et les valeurs de l'index d'oxygène un peu plus faibles (ΔIO = – 25) que celles mesurées dans les carottes proximales. Les études isotopiques (C/N ~ 14 et δ13Corg autour de –26 ‰) et palynologiques indiquent que la matière organique est constituée au 2/3 de particules terrigènes de petite taille (débris ligno-cellulosiques et particules carbonisés et oxydées) et que le restant correspond à un matériel phytoplanctonique amorphe assez fortement dégradé. La taille moyenne de chaque classe de particule organique est estimée quantitativement sur les préparations palynologiques puis comparée aux caractéristiques granulométriques de la fraction organique (grain moyen, asymétrie, etc) définies grâce à un microgranulomètre laser. La comparaison de ces résultats avec les caractéristiques sédimentologiques du sédiment total devrait permettre de dégager les lois de transport des particules organiques par comparaison avec leurs homologues minéraux. Cette connaissance est fondamentale pour intégrer la fraction organique terrigène dans les modèles déterministes d'organisation stratigraphique des dépôts.
(25/08/2026)
MNHN, UPMC, CNRS, ISTO, INSU - CNRS, UO, CNRS, GM, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Spatio-temporal changes in totally and enzymatically hydrolyzable amino acids of superficial sediments from three contrasted areas
(Progress in Oceanography. vol. 65, n° 0079-6611, pp. 89-111, 25/08/2026)
LOBB, OOB, UPMC, CNRS, UPMC, INSU - CNRS, CNRS, IMARPE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LGE, UPD7, IPG Paris