Erosional unconformity or non-deposition? An alternative interpretation of the Eocene seismic stratigraphy offshore Wilkes Land, East Antarctica

The sedimentary stratigraphy along the conjugate Australian-Antarctic continental margins provide insights into their tectonic evolution as well as changes in paleoceanographic conditions in the Southern Ocean. A comprehensive network of multichannel seismic reflection data as well as geological information from drill cores have been used to interpret the stratigraphic evolution of these margins. However, a number of alternative seismic interpretations exist for the Antarctic side, particularly due to sparse drill core information. A prominent high-amplitude reflector observed along the margin, extending from the continental shelf to the foot-of-slope, is at the centre of debate. Recently, two major hiatuses (from 33.6 - 47.9 Ma and 51.06 - 51.9 Ma) were recovered by the IODP drill core U1356A offshore Wilkes Land and correlated to this prominent reflector. Previous seismic stratigraphic investigations interpreted this structure as an erosional unconformity and proposed different events as a possible cause for this formation, including first arrival of the continental glaciation at the coast at about 34 Ma, increase in spreading rate between Australia and Antarctica at about 45 Ma and drastic global sea level drop of 70 m at about 43 Ma. However, such a large-scale erosion must consequently lead to a re-deposition of a significantly large amount of sediment somewhere along the margins, but, to date, no such deposition is observed in the seismic reflection data. Here, we present an alternative seismo-stratigraphic interpretation based on correlation to the sedimentary structures along the Australian margin.We argue that the prominent unconformity is formed due to non-deposition of sediment between �47.8 and �33.6 Ma. The sedimentary units underlying this unconformity show strong similarities in structure, seismic characteristics and variation along the margin with sequences that are partly exposed to the seafloor at the foot of the Australian slope. On the Australian flank, the age of these exposed sediment sequences ranges from �65 Ma to �45 Ma. Low to no sedimentation from 45 Ma to the present-day offshore Australia has been interpreted to explain the exposure of these old sediment units. We propose that non-deposition occurred along both margins from �45 Ma, until large-scale glacial deposition started at 33.6 Ma along the Antarctic margin. Using our new interpretation, we create paleo-bathymetric reconstructions using the software BALPAL at �83 Ma, �65 Ma and �45 Ma. The resulting paleo-bathymetric maps provide essential information, e.g. for paleo–oceanographic and –climatic investigations in the Southern Ocean

The spatial and temporal evolution of strain during the separation of Australia and Antarctica

A re-evaluation of existing onshore and offshore gravity, magnetic, seismic reflection, and well data from the Australo-Antarctic margins suggests that magmatism and along-strike lithospheric heterogeneities have influenced the localization of initial rifting. The 3D crustal architecture of the Australian and Antarctic margins, which formed during multiple rifting episodes spanning ~80 My, reveal local asymmetries along strike. Rift structures from the broad, late Jurassic (165-145 Ma) rift zone are partially overprinted by a narrower, mid-to-late Cretaceous rift zone ~100 Ma, which evolved in highly extended crust. This late-stage rift zone is located within a region of heterogeneous crust with faults that cut late syn-rift strata, interpreted as a continent ocean transition zone. This late stage transitional rift is populated by seismically identified rift-parallel basement highs and intra-crustal bodies with corresponding positive Bouguer gravity and magnetic anomalies. These undrilled features can be interpreted as exposures of exhumed mantle rocks, lower crustal rocks and/or as discrete magmatic bodies. Our results suggest that strain across an initially broad Australo-Antarctic rift system (165-145 Ma) migrated to a narrow rift zone with some magmatism at 100-83 Ma. Breakup did not occur until ~53 Ma within the eastern Bight-Wilkes and Otway-Adélie margin sectors, suggesting a west to east propagation of seafloor spreading. The prolonged eastwards propagation of seafloor spreading processes and the increased asymmetry of the Australian-Antarctic margins coincides with a change from rift-perpendicular to oblique rifting processes, which in turn coincide with along- strike variations in cratonic to Palaeozoic lithosphere

Workplace incivility and work outcomes:Cross-cultural comparison between Australian and Singaporean employees

Workplace incivility is a common issue experienced by employees around the globe. However, research has found cultural variability in how workplace incivility is perceived and interpreted. Studies have shown that employees from high power distance societies tend to be more accepting of workplace mistreatment than employees from low power distance societies. Adopting Conservation of Resources (COR) theory and national culture as theoretical frameworks, we tested a moderated mediation model that linked the experience of workplace incivility, burnout/exhaustion, job satisfaction and work withdrawal between Australian and Singaporean white‐collar employees. Data were collected through an online survey of 301 Australian and 303 Singaporean employees. Results indicated that workplace incivility contributed to burnout/exhaustion, which in turn predicted employees’ job dissatisfaction and work withdrawal. Specifically, Australians were more negatively affected by workplace incivility than Singaporeans. The findings suggest the need to consider employees’ national culture/ethnicity when examining relationships between mistreatment in different workplaces and the outcomes

Anticoagulation Strategies in Non–Critically Ill Patients with Covid-19

BackgroundOptimal thromboprophylaxis for hospitalized patients with coronavirus disease 2019 (Covid-19) is uncertain.MethodsIn an open-label, adaptive platform trial, we randomly assigned hospitalized adults with Covid-19 to low-dose low-molecular-weight heparin thromboprophylaxis or intermediate-dose or low-dose plus aspirin. In response to external evidence, the aspirin intervention was discontinued and a therapeutic-dose arm added. The primary end point was death or the requirement for new organ support by day 28, analyzed with a Bayesian logistic model. Enrolment was closed as a result of operational constraints.ResultsBetween February 2021 and March 2022, 1574 patients were randomly assigned. Among 1526 participants included in the analysis (India, n=1273; Australia and New Zealand, n=138; and Nepal, n=115), the primary outcome occurred in 35 (5.9%) of 596 in low-dose, 25 (4.2%) of 601 in intermediate-dose, 20 (7.2%) of 279 in low-dose plus aspirin, and 7 (14%) of 50 in therapeutic-dose anticoagulation. Compared with low-dose thromboprophylaxis, the median adjusted odds ratio for the primary outcome for intermediate-dose was 0.74 (95% credible interval [CrI], 0.43 to 1.27; posterior probability of effectiveness [adjusted odds ratioConclusionsIn hospitalized non–critically ill adults with Covid-19, compared with low-dose, there was an 86% posterior probability that intermediate-dose, 65% posterior probability that low-dose plus aspirin, and a 7% posterior probability that therapeutic-dose anticoagulation reduced the odds of death or requirement for organ support. No treatment strategy met prespecified stopping criteria before trial closure, precluding definitive conclusions. (Funded by Australian National Health and Medical Research Council or Medical Research Future Fund Investigator and Practitioner Grants and others; ClinicalTrials.gov number, NCT04483960.