How the atlas dates deep-time change

Bracket oxygenation, do not invent an instant

Dated igneous units and sulfur-isotope change bracket the onset of the Great Oxidation interval, while ocean basins followed different redox histories.

The bracket dates a proxy transition, not one global oxygen switch.

Place Avalon fossils above dated ice

Zircon ages order the Gaskiers glaciation and the younger Avalon assemblages; they do not directly date the origin of animals.

A regional measured succession is not a global FAD.

Separate fossil pattern from explanatory model

Cambrian body fossils, traces and disparity document a radiation, but ecological and developmental explanations remain competing syntheses.

Compare regional diversification curves

Ordovician richness and ecological expansion emerge at different rates among regions and groups rather than at one global timestamp.

Read the Meishan extinction interval

Dated ash beds constrain the principal extinction pulse in one reference section to roughly sixty thousand years, with stated analytical uncertainty.

A calibrated reference section is not every ecosystem worldwide.

Recovery unfolds in stages

Triassic recovery differs among ecosystems, guilds and regions; a review synthesis organizes those records without turning them into a single measured event.

Test impact–extinction synchrony

Boundary geochemistry identifies impact ejecta and radioisotopic comparison resolves impact and extinction as synchronous within the published precision.

Synchrony at this resolution does not make every last fossil simultaneous.

Track warming with coupled proxies

Carbon-isotope, temperature and biotic records describe the PETM perturbation, while magnitude and duration remain proxy- and age-model-sensitive.

Compare extinction hypotheses without one cause

Late-Quaternary megafaunal losses vary across continents; comparative models test climate and human influence without observing one universal mechanism.