Researchers identify million-year orbital cycles as ‘pacemaker’ for Earth’s ancient oxygenation pulses

More evidence of these underlying long-term effects on Earth’s climate system. By ‘million-year’ they mean this: ‘The results uncovered long-period cycles of 1.2, 2.6, and 4.5 million years, matching the frequencies of known long-term orbital cycles.’ The known 1.2 million year cycle looks like the period where 3 long term = 13 short term eccentricity cycles (1.237 million tropical years), as other researchers have found. See also the ‘124 kyr’ section in this recent Talkshop post. The article refers to the use of the ‘SCION model: ‘SCION (Spatial Continuous IntegratiON) is a global climate-biogeochemical model that runs over geological timescales.’ [More details at the link].
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A research team from the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences (NIGPAS), along with collaborators, has found that long-term orbital variations occurring over million-year timescales may have served as the “pacemaker” for Earth’s ancient oxygenation pulses, says Phys.org.

Their findings were recently published in Geophysical Research Letters.

The Cambrian Explosion stands as one of the milestones in Earth’s evolutionary history, a period when nearly all modern animal phyla emerged rapidly.

Fossil and geochemical evidence show that the diversification of early Cambrian animals unfolded in multiple evolutionary pulses, paired with synchronous fluctuations in seawater inorganic carbon and sulfate sulfur isotopes.

These variations are widely interpreted as markers of periodic oxygenation events in the atmosphere and shallow oceans. However, the driving force behind these rhythmic oxygen pulses has long remained unclear.

To fill this knowledge gap, the team launched a study in 2019 on well-preserved early Cambrian carbonate successions from the southeastern Siberian Platform. Their analysis revealed that between approximately 524 and 514 million years ago (early Cambrian), marine animal diversity fluctuated periodically every 2–3 million years, which aligned with shifts in seawater carbon and sulfur isotopes.

The team proposed that cyclic changes in the global burial of organic carbon and pyrite drove periodic variations in oxygen levels in the atmosphere and shallow marine environments, in turn shaping the evolutionary dynamics of early marine animals.

Building on this work, the team’s latest research further suggests that these million-year-scale environmental oscillations were likely triggered by long-period orbital variations. Changes in Earth’s orbital configuration altered the distribution of solar radiation across latitudes, leading to periodic climate shifts.
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By integrating orbitally driven climate forcing into the SCION Earth system box model for the first time, the researchers successfully replicated the observed synchronous periodic variations in seawater carbon and sulfur isotopes. This outcome confirms the plausibility of an orbitally forced oxygenation mechanism.

Full article here.
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Image: Location of the Siberian Platform