Basement-cover relations and internal structure of the Cape Smith klippe: A 1.9 Ga greenstone belt in northern Quebec, Canada

The Cape Smith Belt is a 380x60 km tectonic klippe composed of greenschistto amphibolite-grade mafic and komatiitic lava flows and fine-grained quartzose sediment, intruded by minor syn- to post-tectonic granitoids. Previously studied transects in areas of relatively high structural level show that the belt is constructed of seven or more north-dipping thrust sheets which verge toward the Superior Province (Archean) foreland in the south and away from an Archean basement massif (Kovik Antiform) external to the Trans-Hudson Orogen (Early Proterozoic) in the north. A field project (mapping and structural-stratigraphic-metamorphic studies) directed by MRS was begun in 1985 aimed at the structurally deeper levels of the belt and underlying basement, which are superby exposed in oblique cross-section (12 km minimum structural relief) at the west-plunging eastern end of the belt. Mapping now complete of the eastern end of the belt confirms that all of the metavolcanic and most of the metasedimentary rocks are allochthonous with respect to the Archean basement, and that the thrusts must have been rooted north of Kovik Antiform. The main findings follow

Structural and metamorphic architecture of the Zanskar Himalaya, Suru Valley region, NW India: Implications for the evolution of the Himalayan metamorphic core

New 1:50,000-scale geological mapping in the Zanskar Himalaya of NW India, covering 2,400 km2, is integrated with structural and petrographic analysis to document the evolution and key tectonometamorphic relationships within the Himalayan metamorphic core. The integrated dataset constrains the regional three-dimensional geology and relationships between lithostratigraphy, folds, faults, deformation fabrics, metamorphic isograds, and growth of porphyroblasts within the context of five main deformation phases. Following the initial collision of India and Asia, NW−SE-oriented deformation is recorded by D1 (greenschist-facies) fabrics and D2 (greenschist- to amphibolite-facies) fabrics. D2 represents the main tectonometamorphic deformation phase associated with crustal thickening and produced the dominant regional penetrative fabric through crenulation and transposition of D1 fabrics. Thrust-sense D2 fabrics were reactivated during D3 as the Greater Himalayan Sequence was exhumed along the normal-sense Zanskar Shear Zone, which is part of the South Tibetan Detachment System. D3 fabrics, associated with movement on the Zanskar Shear Zone, were temporally continuous with crenulation and mesoscale folding, recording progressive kilometer-scale backfolding and backthrusting toward the NE between the Greater Himalayan Sequence−Tethyan Himalayan Sequence and the adjacent Indus Suture Zone. Finally, D4 and D5 are recorded as kilometer-scale open folding of older planar and linear structures. The orientation of mineral isograd surfaces ranges from subparallel to oblique with respect to D2 planar structural elements. The growth of pelitic and metabasic peak metamorphic phases from greenschist to upper-amphibolite facies is synchronous with or postdates D2 fabrics. D3 fabrics wrap thermal peak porphyroblasts and realign linear mineral phases. Tectonic thinning adjacent to D3 normal faults is documented by reduced structural spacing of isograds and alignment of isograd surfaces parallel to the faults. D4 and D5 structures modify the trace of all regional metamorphic isograds. Collectively, these observations imply that the thermal peak of metamorphism was reached after the main phase of deformation (D2), and predated movement on the Zanskar Shear Zone (D3). The results document numerous classical elements of collisional orogenesis, including implied clockwise P-T paths, polyphase deformation, and a complete Barrovian metamorphic isograd sequence supplemented by complementary metabasic isograds. The Zanskar Himalaya, unlike other areas of the Himalayan metamorphic core, records metamorphic conditions primarily attained following substantial crustal thickening rather than during subsequent decompression and exhumation. The reduced expression and/or discontinuous nature of exhuming fault systems, which produces variable levels of crustal exposure, may account for this lateral heterogeneity across the mountain belt. Deciphering the complex kinematics of continental tectonics requires the integration of observations and data over large length scales and a range of structural levels

Influence of the n-p asymmetry on decay properties of palladium isotopes

The INDRA 4 π-array was coupled with the high acceptance spectrometer VAMOS to study the decay of palladium isotopes with a large range of N/Z = 1–1.26, produced in the 34,36,40Ar + 58,60,64Ni reactions at E/A = 13 .3MeV. The coupling of both apparatuses gives the opportunity to detect complete events with light charged particles identified in INDRA and the compound nucleus residue in VAMOS. The detailed studies of this experiment put constraints on the N/Z effects in the statistical models

Diverse Misinformation: Impacts of Human Biases on Detection of Deepfakes on Networks

Social media platforms often assume that users can self-correct against misinformation. However, social media users are not equally susceptible to all misinformation as their biases influence what types of misinformation might thrive and who might be at risk. We call "diverse misinformation" the complex relationships between human biases and demographics represented in misinformation. To investigate how users' biases impact their susceptibility and their ability to correct each other, we analyze classification of deepfakes as a type of diverse misinformation. We chose deepfakes as a case study for three reasons: 1) their classification as misinformation is more objective; 2) we can control the demographics of the personas presented; 3) deepfakes are a real-world concern with associated harms that must be better understood. Our paper presents an observational survey (N=2,016) where participants are exposed to videos and asked questions about their attributes, not knowing some might be deepfakes. Our analysis investigates the extent to which different users are duped and which perceived demographics of deepfake personas tend to mislead. We find that accuracy varies by demographics, and participants are generally better at classifying videos that match them. We extrapolate from these results to understand the potential population-level impacts of these biases using a mathematical model of the interplay between diverse misinformation and crowd correction. Our model suggests that diverse contacts might provide "herd correction" where friends can protect each other. Altogether, human biases and the attributes of misinformation matter greatly, but having a diverse social group may help reduce susceptibility to misinformation.Comment: Supplementary appendix available upon request for the time bein

Crustal-Lithospheric structure, geological evolution and continental extrusion of Tibet

Abstract HKT-ISTP 2013 A

Baffin Bay paleoenvironments in the LGM and HS1: Resolving the ice-shelf question

Core HU2008029-12PC from the Disko trough mouth fan on the central West Greenland continental slope is used to test whether an ice shelf covered Baffin Bay during the Last Glacial Maximum (LGM) and at the onset of the deglaciation. We use benthic and planktic foraminiferal assemblages, stable isotope analysis of planktic forams, algal biomarkers, ice-rafted detritus (IRD), lithofacies characteristics defined from CT scans, and quantitative mineralogy to reconstruct paleoceanographic conditions, sediment processes and sediment provenance. The chronology is based on radiocarbon dates on planktic foraminifers using a ∆ R of 140 ± 30 14C years, supplemented by the varying reservoir estimates of Stern and Lisiecki (2013) that provide an envelope of potential ages. HU2008029-12PC is bioturbated throughout. Sediments between the core base at 11.3 m and 4.6 m (LGM through HS1) comprise thin turbidites, plumites and hemipelagic sediments with Greenlandic provenance consistent with processes active at the Greenland Ice Sheet margin grounded at or near the shelf edge. Abundance spikes of planktic forams coincide with elevated abundance of benthic forams in assemblages indicative of chilled Atlantic Water, meltwater and intermittent marine productivity. IRD and IP25 are rare in this interval, but brassicasterol, an indicator of marine productivity reaches and sustains low levels during the LGM. These biological characteristics are consistent with a sea-ice covered ocean experiencing periods of more open water such as leads or polynyas in the sea ice cover, with chilled Atlantic Water at depth, rather than full ice-shelf cover. They do not support the existence of a full Baffin Bay ice shelf cover extending from grounded ice on the Davis Strait. Initial ice retreat from the West Greenland margin is manifested by a pronounced lithofacies shift to bioturbated, diatomaceous mud with rare IRD of Greenlandic origin at 467 cm (16.2 cal ka BP; ∆ R = 140 yrs) within HS1. A spike in foraminiferal abundance and ocean warmth indicator benthic forams precedes the initial ice retreat from the shelf edge. At the end of HS1, IP25, brassicasterol and benthic forams indicative of sea-ice edge productivity increase, indicating warming interstadial conditions. Within the Bølling/Allerød interstadial a strong rise in IP25 content and IRD spikes rich in detrital carbonate from northern Baffin Bay indicate that northern Baffin Bay ice streams were retreating and provides evidence for increased open water, advection of Atlantic Water in the West Greenland Current, and formation of an IRD belt along the W. Greenland margin