This work doesn't "solve" the cause of the LJE, but it does provide clean constraints that explanatory models must match. All of the data, models, and code is open source so others can build on it: github.com/sedmonsond/s...

Additionally, Stacey ran her inference separately for deep, intermediate, and shallow depositional environments, and the LJE (a long-lived positive excursion) appears in each.

This revised timing puts the start of the δ¹³C rise before or around the earliest clear signs of oxygenation, tightening the temporal link between the LJE and the Great Oxidation Event.

The timing of the LJE also shifts earlier than many common depictions. Best estimate: it begins around 2,445 million years ago, peaks near 2,130 Ma, and returns toward baseline by about 2,018 Ma.

The main result is that the excursion does look global, but the global peak is more modest than the most extreme local δ¹³C values suggest. In other words, some basins likely amplify the signal beyond what the whole ocean was doing.

Stacey’s approach was to build a statistical model that asks what common signal exists amongst global records of the LJE, if any, while explicitly accounting for the age uncertainty of these records.

However, the cause, and global nature of the LJE remain contentious due to significant uncertainties in the excursion’s timing and magnitude, as well as the the incomplete and spatially variable nature of the shallow-water sedimentary record.

The Lomagundi-Jatuli excursion (LJE) describes an interval of unusual carbon isotope ratios (high δ¹³C) that are broadly the same age as the sediments that record the rise of atmospheric oxygen during the Great Oxidation Event.

As a quick primer: carbon comes in two (isotopic) forms, and the ratio of these two forms in the ocean is controlled by the way that carbon enters, reacts, and leaves Earth's surface. This ratio gets stored in carbonate sediments, so the rock record gives clues about how the ancient carbon worked.

4/4 Fun backstory: this idea started as a final project in our Advanced Sedimentology & Stratigraphy course (EOS 423) at UVic (@seos-uvic.bsky.social). Really fun to see the classroom project grow into a full paper, and I learned a lot about numerical modeling and stratigraphy along the way!

3/4 A key prediction is that transport-driven isotope excursions should occur in very specific stratigraphic contexts: tied to changes in the coastline (transgression/regression). If the same signal appears outside those contexts, a global driver is more likely.

2/4 We built a simple numerical sediment-transport model to track tracers (like δ13C of carbonates) through sediment formation, transport, erosion and deposition. The key result: erosion, reworking, and lateral transport alone can generate stratigraphically correlative isotope excursions.

I really wonder what the GOP's vision of America in 30 years is. Do they want a country that doesn't do fundamental research, without the world's best research universities, with the citizens working in factories assembling iPhone cases?

your papers and teaching material were a great resource and inspiration for me when I designed my 2nd year geochemistry course. thank you for your work! 🏳️‍⚧️

🧐.. this is very true 😐