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ABSTRACT The Bogda Mountains, Xianjiang Uygur Autonomous Region, western China, expose an uppermost Permian–Lower Triassic succession of fully continental strata deposited across three graben (half graben) structures in the mid-paleolatitudes of Pangea. A cyclostratigraphy scheme developed for the succession is subdivided into three low-order cycles (Wutonggou, Jiucaiyuan, Shaofanggou). Low-order cycles are partitioned into 1838 high-order cycles based on repetitive environmental changes, and their plant taphonomic character is assessed in > 4700 m of high-resolution, measured sections distributed across ∼ 100 km. Four taphonomic assemblages are represented by: permineralized wood (both autochthonous and allochthonous), megafloral adpressions (?parautochthonous and allochthonous) identifiable to systematic affinity, unidentifiable (allochthonous) phytoclasts concentrated or disseminated on bedding, and (autochthonous) rooting structures of various configurations (carbon films to rhizoconcretions). Their temporal and spatial occurrences vary across the study area and are dependent on the array of depositional environments exposed in any particular locality. Similar to paleobotanical results in other fully continental basins, megafloral elements are rarely encountered. Both wood (erect permineralized stumps and prostrate logs) and adpressions are found in < 2% of meandering river and limnic cycles, where sediment accumulated under semi-arid to humid conditions. The absence of such assemblages in river-and-lake deposits is more likely related to physical or geographical factors than it is to an absence of organic-matter contribution. With such a low frequency, no predictable pattern or trend to their occurrence can be determined. This is also true for any horizon in which rooting structures are preserved, although paleosols occur in all or parts of high-order cycles developed under arid to humid conditions. Physical rooting structures are encountered in only 23% of these and are not preserved equally across space and time. Allochthonous phytoclasts are the most common taphonomic assemblage, preserved in association with micaceous minerals on bedding in fine-grained lithofacies. The consistency of phytoclast assemblages throughout the succession is empirical evidence for the presence of riparian vegetation during a time when models propose the catastrophic demise of land plants, and does not support an interpretation of vegetational demise followed by long-term recovery across the crisis interval in this basin. These mesofossil and microfossil (palynological) assemblages offer the best opportunity to understand the effects of the crisis on the base of terrestrial ecosystems. 

The Junggar and Turpan basins of Xinjiang, northwest China, host a well-preserved terrestrial Permo-Triassic boundary sequence exposed on the flanks of the Bogda Mountains. During the Permo-Triassic, this region was located in mid-latitude northeast Pangaea (~45°N), making it an important comparison to the higher latitude record preserved in the South African Karoo Basin (~60°S). Broad similarities exist between the tetrapod records of both areas, such as the reported co-occurrence of Dicynodon-grade dicynodontoids and Lystrosaurus in the upper Permian and the high abundance of Lystrosaurus in the Lower Triassic. In the Bogda sections, the Permo-Triassic boundary falls within the upper Guodikeng Formation (= upper Wutonggou low order cycle), but several horizons have been proposed based on biostratigraphy, chemostratigraphy, and paleomagnetic data. A new Bayesian age model calibrated by multiple radiometric dates and tied to detailed litho- and cyclostratigraphic data offers new insight into the location of the Permo-Triassic boundary in Xinjiang and the opportunity to reconsider tetrapod occurrences in a highly resolved chronostratigraphic framework. We investigated the positions of new and historic tetrapod specimens relative to the revised Permo-Triassic boundary, including uncertainties about the locations of key historic specimens. The stratigraphic range of Dicynodon-grade dicynodontoids in Xinjiang is poorly constrained: most specimens, including the holotype of Jimusaria sinkianensis, cannot be precisely placed relative to the Permo-Triassic boundary. A new specimen of Turfanodon sp. for which we have reliable data occurs in the upper Permian. Despite their previous treatment as Permian in age, most Bogda chroniosuchians were collected in strata above the Permo- Triassic boundary and the therocephalian Dalongkoua fuae also may be Triassic. Some prior placements of the Permo- Triassic boundary in Xinjiang imply an upper Permian lowestoccurrence for Lystrosaurus, but all Lystrosaurus specimens that we can precisely locate fall above the Permo-Triassic boundary. The high abundance of Lystrosaurus in the Early Triassic of Xinjiang likely parallels an Early Triassic age for the interval of greatest Lystrosaurus abundance in the Karoo Basin, but additional research is needed to determine whether there was a single, globally synchronous time of highest Lystrosaurus abundance. 

Abstract Lacustrine dolomite nucleation commonly occurs in modern and Neogene evaporitic alkaline lakes. As a result, ancient lacustrine microcrystalline dolomite has been conventionally interpreted to be formed in evaporitic environments. This study, however, suggests a non‐evaporitic origin of dolomite precipitated in a volcanic–hydrothermal lake, where hydrothermal and volcanic processes interacted. The dolomite occurs in lacustrine fine‐grained sedimentary rocks in the middle Permian Lucaogou Formation in the Santanghu intracontinental rift basin, north‐west China. Dolostones are composed mainly of nano‐sized to micron‐sized dolomite with a euhedral to subhedral shape and a low degree of cation ordering, and are interlaminated and intercalated with tuffaceous shale. Non‐dolomite minerals, including quartz, alkaline feldspars, smectite and magnesite mix with the dolomite in various proportions. The 87 Sr/ 86 Sr ratios (0.704528 to 0.705372, average = 0.705004) and δ 26 Mg values (−0.89 to −0.24‰, average = −0.55‰) of dolostones are similar to those of mantle rocks, indicating that the precipitates mainly originated from fluids that migrated upward from the mantle and were subject to water–rock reactions at a great depth. The δ 18 O values (−3.1 to −22.7‰, average = −14.0‰) of the dolostones indicate hydrothermal influence. The trace and rare earth element concentrations suggest a saline, anoxic and volcanic–hydrothermally‐influenced subaqueous environment. In this subaqueous environment of Lucaogou lake, locally high temperatures and a supply of abundant Mg 2+ from a deep source induced by volcanic–hydrothermal activity formed favourable chemical conditions for direct precipitation of primary dolomite. This study's findings deepen the understanding of the origin and processes of lacustrine primary dolomite formation and provide an alternative possibility for environmental interpretations of ancient dolostones. 

Understanding SARS-CoV-2 transmission within and among communities is critical for tailoring public health policies to local context. However, analysis of community transmission is challenging due to a lack of high-resolution surveillance and testing data. Here, using contact tracing records for 644,029 cases and their contacts in New York City during the second pandemic wave, we provide a detailed characterization of the operational performance of contact tracing and reconstruct exposure and transmission networks at individual and ZIP code scales. We find considerable heterogeneity in reported close contacts and secondary infections and evidence of extensive transmission across ZIP code areas. Our analysis reveals the spatial pattern of SARS-CoV-2 spread and communities that are tightly interconnected by exposure and transmission. We find that locations with higher vaccination coverage and lower numbers of visitors to points-of-interest had reduced within- and cross-ZIP code transmission events, highlighting potential measures for curtailing SARS-CoV-2 spread in urban settings.

 

To support COVID-19 pandemic planning, we develop a model-inference system to estimate epidemiological properties of new SARS-CoV-2 variants of concern using case and mortality data while accounting for under-ascertainment, disease seasonality, non-pharmaceutical interventions, and mass-vaccination. Applying this system to study three variants of concern, we estimate that B.1.1.7 has a 46.6% (95% CI: 32.3–54.6%) transmissibility increase but nominal immune escape from protection induced by prior wild-type infection; B.1.351 has a 32.4% (95% CI: 14.6–48.0%) transmissibility increase and 61.3% (95% CI: 42.6–85.8%) immune escape; and P.1 has a 43.3% (95% CI: 30.3–65.3%) transmissibility increase and 52.5% (95% CI: 0–75.8%) immune escape. Model simulations indicate that B.1.351 and P.1 could outcompete B.1.1.7 and lead to increased infections. Our findings highlight the importance of preventing the spread of variants of concern, via continued preventive measures, prompt mass-vaccination, continued vaccine efficacy monitoring, and possible updating of vaccine formulations to ensure high efficacy.