Analysis of 16 marine Permian-Triassic boundary sections with a near-global distribution demonstrates systematic changes in sediment fluxes and lithologies in the aftermath of the end-Permian crisis. Sections from continent-margin and platform settings exhibit higher bulk accumulation rates (BARs) and more clay-rich compositions in the Griesbachian (earliest Triassic) relative to the Changhsingian (latest Permian). These patterns, which largely transcend regional variations in tectonic setting, sequence stratigraphic factors, and facies, are hypothesized to have resulted from a substantial (average ∼7×) increase in the flux of eroded material from adjacent land areas owing to accelerated rates of chemical and physical weathering as a function of higher surface temperatures, increased acidity of precipitation, and changes in landscape stability tied to destruction of terrestrial ecosystems. This sediment surge may have been a contributory factor to the latest Permian marine biotic crisis as well as to the delayed recovery of Early Triassic marine ecosystems owing to the harmful effects of siltation and eutrophication. Contemporaneous deep-sea sections show no increases in sediment flux across the Permian-Triassic boundary owing to their remoteness from continental siliciclastic sources and location below the paleo–carbonate compensation depth.

The rise of oxygen: To understand the evolution of the biosphere, we need to know how much oxygen was present in Earth's atmosphere during most of the past 2.5 billion years. However, there are few proxies sensitive enough to quantify O ₂ at the low levels present until slightly less than 1 billion years ago. Lu et al. measured iodine/calcium ratios in marine carbonates, which are a proxy for dissolved oxygen concentrations in the upper ocean. They found that a major, but temporary, rise in atmospheric O ₂ occurred at around 400 million years ago and that O ₂ levels underwent a step change to near-modern values around 200 million years ago. Science , this issue p. 174