On impact and volcanism across the Cretaceous-Paleogene boundary

The cause of the end-Cretaceous mass extinction is vigorously debated, owing to the occurrence of a very large bolide impact and flood basalt volcanism near the boundary. Disentangling their relative importance is complicated by uncertainty regarding kill mechanisms and the relative timing of volcanogenic outgassing, impact, and extinction. We used carbon cycle modeling and paleotemperature records to constrain the timing of volcanogenic outgassing. We found support for major outgassing beginning and ending distinctly before the impact, with only the impact coinciding with mass extinction and biologically amplified carbon cycle change. Our models show that these extinction-related carbon cycle changes would have allowed the ocean to absorb massive amounts of carbon dioxide, thus limiting the global warming otherwise expected from postextinction volcanism

Paleomagnetism of Rumuruti chondrites suggests a partially differentiated parent body

International audienceDifferent types of magnetic fields were at work in the early solar system: nebular fields generated within the protoplanetary nebula, solar fields, and dynamo fields generated within the solar system solid bodies. Paleomagnetic studies of extraterrestrial materials can help unravel both the history of these magnetic fields, and the evolution of solar system solid bodies. In this study we studied the paleomagnetism of two Rumuruti chondrites (PCA 91002 and LAP 03639). These chondrites could potentially bear the record of the different fields (solar, nebular, dynamo fields) present during the early solar system. The magnetic mineralogy consists of pseudo-single domain pyrrhotite in LAP 03639 and pyrrhotite plus magnetite in PCA 91002. Paleomagnetic analyses using thermal and alternating field demagnetization reveal a stable origin trending component of magnetization. Fields of 12 mu T or higher are required to account for the magnetization in PCA 91002, but the timing and exact mechanism of the magnetization are unconstrained. In LAP 03639, considering various chronological constraints on the parent body evolution and on the evolution of the different sources of magnetic field in the early solar system, an internally-generated (dynamo) field of similar to 5 mu T recorded during retrograde metamorphism is the most likely explanation to account for the measured magnetization. This result indicates the existence of an advecting liquid core within the Rumuruti chondrite parent body, and implies that, as proposed for CV and H chondrites, this chondritic parent body is partially differentiated. (C) 2019 Elsevier B.V. All rights reserved

An early solar system magnetic field recorded in CM chondrites

International audienceWe present a paleomagnetic study of seven CM carbonaceous chondrites. CM chondrites are believed to be some of the most chemically primitive materialsavailable in our solar system and may sample the continuum of transitional objects between asteroids and comets formed in the outer solar system. As such, CM chondrites can help us to understand primordial aspects of the history of the early solar system including protoplanetary disk and planetesimal magnetism.The ferromagnetic assemblage of CM chondrites is composed of a mixture of primary metallic iron, pyrrhotite, and magnetite. The remanent properties are usually dominated by secondary pyrrhotite. Paleomagnetic analyses using thermal and alternating field demagnetization identified a stable origin-trending component of magnetization in the seven studied CM chondrites. In each meteorite, this component is homogeneous in direction at least at the cm scale and is therefore post-accretional. We interpret this stable component as a pre-terrestrial chemical remanent magnetization acquired during crystallization of magnetite and pyrrhotite during parent body aqueous alteration in a field of at least a few μT (2 ±1.5μT).Considering the timescale and intensities of primordial magnetic fields, both internally generated fields from a putative dynamo and external fields, generated in the protoplanetary disk, may have been recorded by CM chondrites. It is presently difficult to discriminate between the two hypotheses. Regardless, CM chondrites likely contain the oldest paleomagnetic record yet identifie

A NEW STREWNFIELD OF SPLASH-FORM IMPACT GLASSES IN ATACAMA, CHILE: A MOSSBAUER

78th Annual Meeting of the Meteoritical-Society, Berkeley, CA, JUL 27-31, 2015International audienc

1022MO Predicting overall survival of patients with melanoma and NSCLC treated with immunotherapy using AI combining total tumor volume and tumor heterogeneity on CT-Scans

International audienceUsing total tumor volume and AI tumor heterogeneity from CT scans, it may be possible to predict the prognosis of oncology patients, identify those who could benefit from immunotherapy, and provide valuable guidance for treatment

142P Correlating total tumor volume on CT-Scan and liquid biopsy ctDNA in 1017 patients with metastatic cancer: A novel study

International audienceLiquid biopsy is an emerging technology capable of detecting cancer, while CT-imaging is the gold standard. We aim to correlate imaging features from CT-scans to liquid biopsy ctDNA tumor fraction (TF) and blood Tumor Mutational Burden (bTMB)

Association of metastatic pattern and molecular status in metastatic lung non-small cell lung cancer adenocarcinomas

BACKGROUND : The recent identification of molecular alterations in some lung adenocarcinomas has led to the emergence of effective targeted therapies thus drastically improving their prognosis.The aim of our study was to investigate the association between driver oncogene alterations and metastatic patterns on imaging assessment, in a large cohort of metastatic lung adenocarcinoma patients. [...

Paleogene Newfoundland sediment drifts

Integrated Ocean Drilling Program Expedition 342 was designed to recover Paleogene sedimentary sequences with unusually high deposition rates across a wide range of water depths (Sites U1403–U1411). The drilling area is positioned to capture sedimentary and geochemical records of ocean chemistry and overturning circulation beneath the flow of the Deep Western Boundary Current in the northwest Atlantic Ocean. In addition, two operational days were dedicated to a sea trial of the Motion Decoupled Hydraulic Delivery System developmental tool (Site U1402). The expedition was primarily targeted at reconstructing the Paleogene carbonate compensation depth (CCD) in the North Atlantic for reference to recently obtained high-fidelity records of the CCD in the equatorial Pacific. The site located in the deepest water (Site U1403) was at a paleodepth of ~4.5 km 50 m.y. ago, whereas the site located in the shallowest water (Site U1408) can be backtracked to a paleodepth of 2.5 km at the same time. The combination of sites yields a record of the history of CCD change over a 2 km depth range from the ocean abyss to middle range water depths. Notable findings include the discovery of intermittent calcareous sediments in the Cretaceous, Paleocene, and early to middle Eocene at 4.5 km paleodepth, suggesting a deep Atlantic CCD during these times. We find evidence of carbonate deposition events following the Cretaceous/Paleogene (K/Pg) boundary mass extinction, the Paleocene/Eocene Thermal Maximum, and the Eocene–Oligocene transition. These deposition events may reflect the rebalancing of ocean alkalinity after mass extinctions or abrupt global climate change. Intervals during which the CCD appears to have been markedly shallow in the North Atlantic include the Early Eocene Climatic Optimum, the late Eocene, and the middle Oligocene. A second major objective of Expedition 342 was to recover clay-rich sequences with well-preserved microfossils and high rates of accumulation in comparison to the modest rates of accumulation (~0.5–1 cm/k.y. in the Paleogene) typically encountered at pelagic sites. As anticipated, Expedition 342 recovered sequences with sedimentation rates of as much as 10 cm/k.y.—high enough to enable studies of the dynamics of past abrupt climate change, including both transitions into “greenhouse” and “icehouse” climate states, the full magnitudes of hyperthermal events, and rates of change in the CCD. We find that the thickest central parts of the various sediment drifts typically record similar depositional packages to those recovered in the thin “noses” and “tails” of these drifts, but these central parts are often massively expanded with clay, especially near the CCD. Times of rapid accumulation of drift deposits include the early Eocene to late middle Eocene, the late Eocene to early Oligocene, the late Oligocene and early Miocene, the later Miocene to probable late Pliocene, and the Pleistocene. Widespread hiatuses are present near the Paleocene/Eocene boundary into the middle early Eocene and the middle Oligocene. The Eocene/Oligocene boundary is a period of slow sedimentation at most sites but is expanded at Site U1411. A marked change in the geometry of drift formation is observed in the ?late Pliocene, as has been observed in drift deposits elsewhere. An unexpected finding was the recovery of a number of Cretaceous “critical boundaries.” These include the K/Pg boundary, the Campanian–Coniacian interval, the Cenomanian–Turonian boundary and oceanic anoxic event (OAE) 2, and the Albian/Cenomanian boundary OAE 1d. These intervals were drilled opportunistically when they were encountered near or above our target depth for a given site. The K/Pg boundary was recovered at Site U1403, where it proved to have a well-preserved, normally graded spherule bed and unusually well preserved earliest Danian planktonic foraminifer community. The Campanian–Coniacian interval was cored at Site U1407 and is unusual mainly for the relative biostratigraphic completeness of a sequence that elsewhere commonly shows hiatuses in the early Campanian. The Cenomanian–Turonian transition was also cored at Site U1407 and consists of a series of organic black shales in nannofossil chalk with as much as 11 wt% total organic carbon (TOC). The Cenomanian–Turonian sequence at Site U1407 is broadly similar in biostratigraphy, sequence of black shales, and sediment color to classic Italian and northern German outcrop sections. Finally, coring at Site U1407 also recovered a lower Cenomanian nannofossil chalk and nannofossil claystone record that extends into the biozones associated with OAE 1d. The Albian–Cenomanian sequence is notable for the generally high quality of microfossil preservation and its gradational contact with underlying Albian shallow-marine carbonate grainstone and packstone. We created high-quality spliced records of most of the sites on Southeast Newfoundland Ridge that penetrate sequences with carbonate-rich lithologies. As anticipated, the task of creating spliced records in the more clay-rich lithologies in some sites was not straightforward due to intervals of low-amplitude change in some physical properties data sets. All sites also proved to have differences in stratigraphy between adjacent holes showing that there is often considerable local variation within the drift sequences. Particularly expanded sedimentary sequences were drilled in Miocene–Oligocene, Eocene–Oligocene, and middle Eocene sequences. Comparison of our drilling results with seismic stratigraphy from the Southeast Newfoundland Ridge indicates large-scale lateral changes in age and thickness of sediment drift packages, regionally meaning that the area presents an attractive target for future expeditions aimed at recovering high deposition–rate records from many parts of the Cenozoic