• Digital Humanities and Cultural Heritage
• CN close
• NZ close
• HAL-UPMC close

We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov-Gerasimenko from before Rosetta's arrival until nearly the end of mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft, and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively `well behaved' comet, typical of Jupiter family comets and with activity patterns that repeat from orbit-to-orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends -- in this paper we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies. Author prepared version; final published version available at journal. 22 pages

Extra sets of 2D multi-channel seismic and chronostratigraphic data allowed us to undertake analyses of source to sink processes and triggering mechanisms of the gigantic megaslides previously documented off the NW and SE steep slope settings of the Foz do Amazonas basin. As these megaslides comprise two sets of stacked allochthonous masses within the Upper Miocene-Quaternary sedimentary record, they are now described as Mass-Transport Complexes (MTCs) and have been renamed the Amapá Megaslide Complex (AMC) and the Pará-Maranhão Megaslide Complex (PMMC). Individual megaslides of both MTCs can mobilize up to kilometre-thick sedimentary series as allochthonous masses with distinct flow directions, degrees of sediment disruption and internal coherence. Megaslides spread downslope over areas as large as thousands of km2, attaining dimensions comparable to the world's largest mass-transport deposits. Among all the megaslides, the basal and largest AM1 megaslide (AMC) stands as a quite unique example of mass-transport deposit in the basin, interpreted as a dominant carbonate allochthonous mass sourced from a mixed carbonate-siliciclastic platform. The instability was probably triggered between the late Miocene and the end of the Early Pliocene by the gravitational collapse of the mixed platform under its own weight, after successive subaerial exposures which generated karstification processes. Siliciclastic-type megaslides, on the other hand, are all sourced from large upslope slide and/or rotated blocks (up to 60 km wide in the case of the PMMC). The detachment of upslope blocks was triggered by structurally-induced seabed movements during the Mid Pliocene-Pleistocene (in the case of the PMMC) and during the Pleistocene (in the case of the AMC). All mapped features support the interpretation of sedimentary blocks which have undergone long lasting deformation, having been variably folded and faulted by the sliding along an overpressured condensed section (H3 horizon). H3 horizon equally acts as the upper décollement level for the gravity tectonic system that operates on the regional scale of the Foz do Amazonas basin. In such a context, the results of this study evidence complex links between variable modes and scales of gravity processes (gravity tectonics and MTCs emplacements), all induced by instability created from a condensed section prone to produce pore fluid overpressure. And yet, seismic attributes of the décollement H3 across the slope, characterized by a reflector of negative polarity of high amplitude, indicate that the potential for similar large scale sediment failures continues to exist across the AMC and PMMC. International audience

AbstractThe Permian–Triassic boundary interval in shallow shelf seas of South China shows Upper Permian limestones overlain by lowermost Triassic microbialites. Global sea‐level rose across the Permian–Triassic boundary, but an irregular top‐Permian erosion surface across a 10 km north–south transect of the Great Bank of Guizhou contains evidence of sea‐level fluctuation. The surface represents the ‘event horizon’ of mass extinction, below the biostratigraphic Permian–Triassic boundary defined by first appearance datum of conodont Hindeodus parvus. An Upper Permian foraminiferal grainstone beneath this surface contains geopetal sediments, etched grains, and pendent and meniscus cements interpreted here as vadose. However, these latter diagenetic processes occurred before the event horizon and were followed by erosion of the final Permian surface. This erosion cuts previous fabrics but lacks evidence of weathering or bioerosion. A few centimetres below is an earlier grainstone that was also eroded but lacks proof of sub‐aerial processes. Samples therefore reveal one, or possibly two, small‐scale relative sea‐level changes before the Triassic transgression in this area, and these may relate to local tectonics. The final Permian surface is subject to at least four interpretations: (i) sub‐aerial physical erosion and dissolution by carbon dioxide‐enriched fresh water or carbon dioxide‐enriched mixed water, prior to Triassic transgression; (ii) sub‐aerial physical erosion overprinted by dissolution related to carbon dioxide‐enriched sea water in the Early Triassic transgression; (iii) submarine dissolution affected by acidified sea water due to rapid increase in volcanically‐derived carbon dioxide and oxidized methane released from marine clathrates; (iv) submarine dissolution due to acid anoxic waters rising across the continental shelf, unrelated to atmospheric carbon dioxide or oxidized methane. Field and petrographic evidence suggests that (i) is the simplest option; and it is possible that (ii) and (iii) occurred, but none are proved. Option (iv) is unlikely given the evidence and modelling of supersaturation of upwelled waters with respect to bicarbonate.

Abstract. Climate and environments of the mid-Pliocene warm period (3.264 to 3.025 Ma) have been extensively studied. Whilst numerical models have shed light on the nature of climate at the time, uncertainties in their predictions have not been systematically examined. The Pliocene Model Intercomparison Project quantifies uncertainties in model outputs through a coordinated multi-model and multi-model/data intercomparison. Whilst commonalities in model outputs for the Pliocene are clearly evident, we show substantial variation in the sensitivity of models to the implementation of Pliocene boundary conditions. Models appear able to reproduce many regional changes in temperature reconstructed from geological proxies. However, data/model comparison highlights that models potentially underestimate polar amplification. To assert this conclusion with greater confidence, limitations in the time-averaged proxy data currently available must be addressed. Furthermore, sensitivity tests exploring the known unknowns in modelling Pliocene climate specifically relevant to the high latitudes are essential (e.g. palaeogeography, gateways, orbital forcing and trace gasses). Estimates of longer-term sensitivity to CO2 (also known as Earth System Sensitivity; ESS), support previous work suggesting that ESS is greater than Climate Sensitivity (CS), and suggest that the ratio of ESS to CS is between 1 and 2, with a "best" estimate of 1.5.

The Roussillon Basin is a non-silled Miocene sedimentary basin filling a late Oligocene–early Miocene graben. The basin was intensively impacted by the 2 Messinian fluvial erosion, as evidenced in exposed sections, in seismic profiles and in deep boreholes drilled for hydrocarbon exploration. As the basin was open to the Mediterranean Sea, the huge drop in sea level at the peak of the Messinian Salinity Crisis is clearly recorded, along with the subsequent sudden marine reflooding and the resulting prograding sedimentary filling, particularly in Gilbert-type fan deltas. Here, the Messinian Erosional Surface (MES) is accurately mapped in a high-resolution document, which corrects the confusion resulting from the set of 1:50,000 scale regional maps. Aim of the 3D reconstruction of the MES is to modernize geological mapping, a crucial challenge for Mediterranean and peripheral areas. Thanks to a reliable chronostratigraphy provided by planktonic foraminifers, calcareous nannofossils, micro-and macro-mammal remains, paleomagnetism and a 10 Be cosmogenic nuclide-derived study, our reconstruction is one of the most comprehensive models of changes in sea level from 6 to 3 Ma. After the marine reflooding of the Mediterranean Basin at 5.46 Ma, the fluctuations in sea level recorded in the Roussillon Basin were forced by global changes. Following reflooding, the Prades large olistostrome collapsed prepared by the previous exhumation along the Canigou fault. The olistostrome is a good example of a local accident resulting from Messinian events. The exceptional changes in sea level at the peak of the Messinian Salinity Crisis deeply marked the Roussillon Basin, momentarily overprinting the Pyrenean orogenesis. Key words: Roussillon Basin – Messinian subaerial erosion –Zanclean sedimentary filling –Prades olistostrome. International audience

In the NW Songliao Basin, NE China, petroleum is produced from fluvio-deltaic sandstones in the Upper Cretaceous Yaojia Formation. Source rocks are dark-colored lacustrine shales of the Qinshankou Formation. In this paper, two models were developed to characterize the petroleum migration pathways in the lower member (Member 1) of the Yaojia Formation. In the first model, which applies to the northern region of the study area, petroleum migrates only in the lowermost carrier bed in Member 1 immediately above the area of the source kitchen, and later in multiple carrier beds outside this area. In the second model, which represents migration patterns in the central and southern regions of the study area, petroleum migrates in multiple carrier beds both within and outside the area of the source kitchen. Pressures in the Yaojia Formation were inferred to be hydrostatic while petroleum expulsion and migration took place. Therefore seven "migration-accumulation" (i.e., local palaeo-drainage) systems were defined according to the fluid potential gradients. Migration loss was found to vary markedly between migration-accumulation systems in the study area, and was controlled by factors including the shape, width and area of the effective source rocks, the thickness and distribution of carrier beds inside the source area, the migration distance outside the source area, and the number of carrier beds involved in petroleum migration. Using these two models, petroleum loss during secondary migration was estimated. The loss during secondary migration was approximately 5.21 billion bbl of petroleum, which is approximately 6% of the petroleum expelled into the first Member of the Yaojia Formation. Nearly 80% of the total migration loss occurred in all the carrier beds above the source area. International audience

Abstract The Lapita colonization, which occurred in the late Holocene, is one of the most remarkable prehistorical human colonizations. To explore the possible influence of El Nino–Southern Oscillation (ENSO) on this event, bulk oxygen (δ 18 O shell ) and carbon (δ 13 C shell ) stable isotope records were obtained from eight fossil Tridacna sp. and Hippopus hippopus giant clams, unearthed from Lapita archeological sites of New Caledonia and Vanuatu. These giant clams were dated ca. 3.8–2.3 ka BP. These δ 18 O shell and δ 13 C shell records were used as proxies for combined sea surface temperature and salinity and precipitation. In addition, geochemical records were obtained from modern conspecifics from New Caledonia to create a baseline against which fossil giant clam records could be compared. The isotopic records revealed the occurrence of two distinct climate states in New Caledonia ca. 3.2–2.3 ka BP: one climate state was characterized by climatic conditions similar to those observed today and the second was comparable to warmer and wetter conditions similar to Vanuatu's modern climate. Considering that previous paleo-climate reconstructions in the West Pacific did not show a shift of the mean climatic state and that they revealed a weak centennial climate variability, our results suggest that the climatic mean state has been alternating between these two states at a decadal or an inter-annual frequency. This strong climate variability recorded in the giant clam shells may reflect an increase in the ENSO variability, supporting the hypothesis of an ENSO-forced Lapita colonization as suggested by Anderson et al. (2006).