Oxygen Levels in the Early Earth’s Atmosphere

“Lack of oxygen did not hold back evolution of complex life” was the bold announcement in the scientific news media on January 26, 2016.1 An opportunity is never lost by the secular media to trumpet as supposed fact the latest scientific findings that so confidently promote the secular, naturalistic, evolutionary worldview of life’s history in a uniformitarian framework and timescale for earth’s history.

This time it was all about the earth’s early atmosphere supposedly being devoid of enough oxygen to fuel the later-claimed evolution of “complex” animals from earlier “simple” life. So what was really found? Does it really show the earth’s early atmosphere was devoid of oxygen? And how does this relate or fit with what God’s Word teaches about the earth’s earliest history when He created everything fully formed and functioning in six literal days?

The Evolutionary-Uniformitarian “Story” About Earth and Life History

To answer these questions, we first need to review the evolutionary-uniformitarian “story” about the earth’s history and the claimed naturalistic development of life on earth to understand what secular scientists believe about how the atmosphere gained its present oxygen content.

Evolutionary geology thinking maintains that when the earth condensed in a hot molten state from the solar nebula about 4.6 Ga (billion years ago) it had no ocean and no atmosphere. As the earth subsequently cooled and outgassed, lots of steam condensed and collected to eventually form the first ocean waters, even by about 4.0 Ga according to the latest claimed evidence.2 Yet there was supposedly only a rudimentary atmosphere to begin with, dominated by gases such as water vapor, carbon dioxide, methane, and ammonia, with virtually no free oxygen. In fact, it is claimed that in the so-called Archean and earliest Proterozoic before 2.3 Ga, that is, for the earth’s first 2.3 billion years, atmospheric oxygen was likely less than 0.001% of present atmospheric levels (PAL).3

Such claims about the makeup of the earth’s early atmosphere are based on indirect evidences, which are interpretations of chemical analyses of sedimentary rocks in today’s world.4 As such, these interpretations are being made by using assumptions about the unobserved past based on what is observed in the present.

These interpretations are being made by using assumptions about the unobserved past based on what is observed in the present.

Furthermore, based on this scenario it is further claimed that the lack of atmospheric oxygen inhibited the evolutionary development of “complex” life. This is because it is estimated that by the beginning of the Phanerozoic, approximately 550 Ma (million years ago), atmospheric oxygen levels had risen to greater than about 20% PAL, sufficient to sustain large-animal respiration.5 Indeed, there is a long-standing suggestion among evolutionists that rising atmospheric oxygen concentrations in the late Neoproterozoic Eon (1,000–542 Ma) enabled animal respiration, thus explaining the timing of animal evolution, which resulted at 542 Ma in the so-called Cambrian explosion.6

So much of this is conjectural. The oxygen levels required for the respiration needed to sustain large motile animals is obviously higher than that needed for supposedly “simple” creatures without eyes, arms, and legs. So evolutionists have believed that when the first such animals supposedly emerged between 800 Ma and 685 Ma, the oxygen levels in the atmosphere were probably ≤ 1%. PAL.7 Yet recent chromium isotope analyses of Precambrian sedimentary rocks are interpreted as suggesting oxygen levels were <0.1% PAL through the Mesoproterozoic Eon (1,600–1,000 Ma) until 700 Ma, when rising levels then spurred animal evolution.8

Results of the New, Different Study

However, using a different approach, the science media announced the claims of a more recent study that at a level of ≥3.8% PAL there was sufficient oxygen in the earth’s atmosphere for animal respiration even 1,400 million years ago.9 This study’s research team analyzed outcrop and drill core samples of the black shale and mudstone beds of Unit 3 of the Xiamaling Formation in Northeastern China for trace metals V (vanadium), Mo (molybdenum), and U (uranium) and organic carbon. These sedimentary rocks are claimed to date at 1.4 Ga, based on U-Pb dating of zircons extracted from a weathered volcanic ash bed near the top of Unit 3.10

To them it demonstrated that there was sufficient oxygen in the atmosphere back then to fuel animal respiration long before the supposed evolution of the animals themselves.

Assuming these sediments were originally deposited in a marine environment at a water depth of >100 meters (330 feet) and assuming the present is the key to the past, the team determined that the enrichment patterns of these trace metals in these beds is consistent with the ocean bottom waters having been oxygenated where these black shales and mudstones were deposited. Furthermore, the biomarkers found in their organic carbon indicated that there must have been green sulfur bacteria in the water column. They then performed simple oceanographic modeling of the marine carbon-oxygen cycle dynamics to show that these geochemical results are consistent with atmospheric oxygen levels ≥3.8% PAL during deposition of these sediments, supposedly 1.4 billion years ago. To them it demonstrated that there was sufficient oxygen in the atmosphere back then to fuel animal respiration long before the supposed evolution of the animals themselves.

An Even More Recent Study with Contradictory Evidence

So how reliable is this latest estimate of the oxygen level in the earth’s atmosphere at 1.4 Ga? Barely three months after this study had been published, the science news media was again trumpeting more about the oxygen levels in the earth’s early atmosphere.11 Yet another paper was published with a radically different estimate, this time suggesting the earth’s upper atmosphere was oxygen-rich during the Archean, at 2.7 Ga, with an oxygen level similar to the earth’s present-day upper atmosphere.12

This research team extracted 60 fossil micrometeorites from a limestone unit in the Pilbara region of northwestern Australia. They chose the limestone layers of the Meentheena Member in the Tumbiana Formation of the Mount Bruce Supergroup in the Hamersley Basin because it is barely affected by subsequent deformation and metamorphism, it is assumed to have been deposited slowly, thereby allowing greater time for accumulation of micrometeorites,13 and limestone is easily dissolved with acid, allowing extraction of the micrometeorites. The reputed age of these limestone beds is 2.721 ± 0.004 Ga, based on zircon U-Pb dating.14

All 60 micrometeorites were identified as cosmic spherules, sand-sized meteoritic material that fully melted during atmospheric entry at 75–90 km (47–56 miles) above the earth’s surface. The FeNi (iron-nickel) metal in them had oxidized while molten to form interlocking dendritic crystals primarily of magnetite (Fe₃O₄), with wüstite (FeO) + FeNi metal sometimes preserved.

The next step in their investigation was to set up a mathematical model to show how the micrometeorites would get oxidized during atmospheric entry. The only molecules they concluded were capable of oxidizing the FeNi metal of the micrometeorites would be O₂ and CO₂. Yet their equilibrium-based calculations showed that these small micrometeorites could not have been oxidized to liquid magnetite by a CO₂-dominated atmosphere, so some O₂ was required to produce the dominant proportions of magnetite and/or wüstite relative to FeNi metal in the micrometeorites. Thus after careful modeling of the stability fields of the relevant mineral species in the presence of the various gaseous atmospheric components, they concluded that the complete oxidation of these very small micrometeorites to magnetite suggests that the Archean upper atmosphere at 2.7 Ga may have been characterized by oxygen levels approaching those of the present-day earth, requiring relatively abundant CO₂ as a source of O₂, and elevated ratios of O₂ to CO.

The corollary to this conclusion they then briefly examined was whether an oxygen-rich upper atmosphere implied an oxygen-rich lower atmosphere as well. However, they deferred to the current models for the Archean lower atmosphere which are based on the sulfur isotopes found in Archean sedimentary rocks that suggest an oxygen level of 0.001% PAL.15 Chemical models of the Archean atmosphere are based on gas fluxes from modern volcanoes because their evolutionary model of the earth requires volcanic outgassing to form its atmosphere. Thus they argue that the reaction of any O₂ at lower atmospheric levels with abundant volcano-derived H₂ gas would supposedly have eliminated free oxygen. To explain the oxygen in the Archean upper atmosphere, they had to conclude that there must have been a strong decoupling of the lower and upper atmosphere at that time, with no mixing due to the methane postulated to have been in the lower atmosphere.16

And Another Study

Even more revealing is yet another study just published.17 In this latest study, air bubbles trapped in salt crystals in a rock unit supposedly 815 million years old in western central Australia were analysed. These air bubbles were assumed to represent the atmospheric air at the time the bubbles got trapped in the salt crystals. That assumption was tested and verified, at least for modern conditions, by analyzing air bubbles trapped in salt crystals forming today in salty ponds and lakes.

Our finding answers one big question, did life come first or atmospheric oxygen; it is the latter.

The study results were very surprising, at least for the uniformitarian (evolutionary) scientists. The air in these bubbles had an average oxygen content of 10.9%, which is slightly more than 50% PAL! To put that into perspective, this means oxygen was very abundant in the earth’s atmosphere well before the supposed evolution of complex animals. Commenting in the Washington Post, reporter Shayla Love wrote that biologists have argued for decades that oxygen was the spark that led to the myriad of new creatures, and that this new study puts millions of years between the two events.18 She quotes Uwe Brand, a coauthor of the technical paper reporting this study: “Our finding answers one big question, did life come first or atmospheric oxygen; it is the latter.”

This latest study was also independently commented on favorably in the same journal in which the study was published.19 In a “Research Focus” article, David Jones of Amherst College in Massachusetts expressed qualified optimism for the significance and validity of this latest study and suggested that it could change the entire landscape for understanding the oxygen content of earth’s early atmosphere. Furthermore, the study’s demonstration that the Neoproterozoic atmosphere had an oxygen content of at least 50% PAL has shown how inadequate are the proxies used in previous studies that estimated woefully lower oxygen levels in the earth’s early atmosphere.

Indeed, before having these air samples to measure, scientists had to estimate ancient levels of oxygen through indirect means, often looking for traces of chemical reactions that required oxygen. By such indirect means, as already discussed above, they had recently determined that supposedly 1,400 million years ago the earth’s atmosphere contained oxygen levels ≥3.8% PAL. But these latest direct measurements have to be regarded as a more certain way of estimating past atmospheric oxygen levels, assuming the air bubbles have not been contaminated or oxygen has not been lost from them in all the supposed millions of years. In any case, it is thus evident that the earth’s atmosphere has always contained abundant oxygen capable of sustaining abundant animal life of all kinds, as indicated by the oxygen levels in these air bubbles trapped in salt crystals in these supposedly 815 million-year-old (that is, probably late pre-Flood) sedimentary layers.

Ignored Global Evidence of Abundant Oxygen Always Being in the Earth’s Atmosphere

However, it has long been demonstrated that the distributions of carbon, sulfur, uranium, and iron (ferric and ferrous) in Precambrian sedimentary rocks are similar to those in Phanerozoic sedimentary rocks, and that therefore the earth’s atmosphere has always been oxidizing.20 These arguments have previously been presented in detail.21 The authors of the original study (Dimroth and Kimberley 1976) stated unequivocally that there is “no evidence in the sedimentary distributions of carbon, sulfur, uranium or iron, that an oxygen-free atmosphere has existed at any time during the span of geological history recorded in well preserved sedimentary rocks” (emphasis mine). They explained that:

The sedimentary distributions of carbon, sulfur, uranium, and ferric and ferrous iron depend greatly upon ambient oxygen pressure and should reflect any major change in proportion of oxygen in the atmosphere or hydrosphere. The similar distributions of these elements in sedimentary rocks of all ages are here interpreted to indicate the existence of a Precambrian atmosphere containing much oxygen.

Indeed, organic carbon contents and distributions are similar in Precambrian and Quaternary sedimentary rocks and sediments, although distributions in both would have been sensitive to variations in rates of organic productivity and atmospheric oxygen pressure. And the constancy of carbon isotopic fractionation in sedimentary rocks is, in fact, an indication of relative constancy of free-oxygen production. Furthermore, the distribution of sulfur in Archaean and Proterozoic rocks is similar to that in Phanerozoic rocks of comparable type.

There are abundant global-scale geological evidences that the earth’s atmosphere has always contained abundant oxygen.

Thus there are abundant global-scale geological evidences that the earth’s atmosphere has always contained abundant oxygen. And these evidences have remained unchallenged since first assembled, in spite of these recent studies, which contradict one another anyway. It clearly demonstrates that local studies that focus on small details using modeling or indirect analytical results as supposed proxies are likely going to be wrong. This is because such local studies focusing on small details always require tenuous assumptions to interpret and then apply the interpretation on a global scale. After all, it is the same in any forensic science, namely, interpretations about the unobserved past should never trump the eyewitness reports. This is especially so when we have God’s testimony of earth’s early history.

Implications of God’s Eyewitness Record of the Earth’s Early History

Genesis 1 tells us that when God made the earth on day one it was covered in water. He didn’t make the atmosphere until day two when he separated the waters and put the expanse between them. While the expanse (Hebrew rāqîa‘) includes outer space, the “face” of it (as seen by later human observers looking up from the earth’s surface) was where God placed the birds to fly on day five.22 So His creation of the expanse on day two included the atmosphere. And even back then it would have contained oxygen levels similar to today’s atmosphere. This is because God’s pattern was to create on earlier days in preparation for what He was going to create on later days. Thus He created the trees already bearing fruit on day three because three days later Adam and Eve would need food. So it is only reasonable that on day two God created the atmosphere containing good oxygen levels in readiness for the birds and animals on Days Five and Six, not forgetting the plants on day three expiring oxygen during photosynthesis.

Then on day three we read in Genesis 1:9–10 that God made the dry land on which He then created soil in which He placed the plants. This must have required catastrophic earth movements and associated plutonism and volcanism, as God took a large area of the crustal rocks from beneath the waters of the global ocean created and formed on the first two days and raised it above the waters to create the land of a supercontinent, as we are told He gathered the waters together into one place which He called seas.23 Such earth movements would have resulted in the emerging land being catastrophically eroded and the sediments transported and deposited offshore.24

The mistake made by secular geologists today is to use today’s processes to explain the formation of the earliest rocks for which God says He used different processes to create.

An important principle should be emphasized here. We can still examine today some of the products of what God created during the Creation Week, such as the earth’s earliest rocks. But we cannot use today’s slow-and-gradual geologic processes to explain their formation. In other words, the present is not the key to the past, because when He created those rocks God did not use present, observable processes to create them. His creative acts were one-time-only, unique, supernatural processes. God subsequently put in place geologic processes of conservation, which we observe today, but those are different from His creation processes. So the mistake made by secular geologists today is to use today’s processes to explain the formation of the earliest rocks for which God says He used different processes to create. It is the same as people in Jesus’ day hypothetically using the properties of the mud Jesus put on the blind man’s eyes to try to explain how the man’s eyesight was restored (John 9:6–7), when in fact it was a supernatural act by Jesus the Creator of eyes to heal the eyes of a man who had been blind from birth.

Applying these constraints from God’s eyewitness account to what we observe in the geologic record today, we would not be surprised if the earliest crustal rocks did not show any evidence of being formed under an atmosphere containing oxygen. And so it is that the earliest rocks, the so-called Hadean and lowermost Archean rocks of what is the crystalline (granitic and metamorphic) basement (or foundational) rocks of the continents, do show conclusive evidence of not being formed under an atmosphere containing oxygen, likely being from God’s initial creation of the earth on day one. However, overlying those rocks are thick sequences of sedimentary and volcanic rocks of the so-called middle-upper Archean and Paleoproterozoic, which contain the fossilized structures called stromatolites built by cyanobacteria.25 These rocks would seem to represent the sediments and volcanics produced catastrophically on day three when the dry land was uplifted, and they clearly display abundant evidence of having formed under an atmosphere containing oxygen levels similar to today’s atmosphere. This is confirmed by their carbon, sulfur, uranium, and ferric and ferrous iron contents and distributions being the same as those in sedimentary rocks deposited during the later global, cataclysmic Flood and since, definitely under an oxidizing atmosphere. And a pre-Flood atmospheric oxygen level similar to today’s level is confirmed by air bubbles trapped in salt crystals in probable pre-Flood sedimentary layers.

Conclusions

The claims of evolutionists about the oxygen levels in the earth’s early atmosphere are based on applying present-day observations and processes to various chemical analyses of sedimentary rocks formed early in the earth’s geologic record. These can only ever be indirect evidences. And due to the wrong assumptions being used to interpret them, it is hardly surprising that they can be, and often are, contradictory. To assume that we can use present, observable processes and rock properties to explain how these earliest rocks formed and to estimate the oxygen content of the atmosphere back then is simply invalid.

The infinite, eternal, all-knowing, all-powerful, personal Creator God tells us in His eyewitness account in Genesis 1 that He used different processes during the Creation Week than what He uses today to operate and conserve the earth and its inhabitants. In six literal days He spoke everything into existence supernaturally so that it was all perfectly formed and functioning as a mature earth and universe. So when He instantly created the atmosphere on day two, it had all the oxygen He intended it to contain for the animals to breathe three to four days (not billions of years) later.

However clever and logical man’s prone-to-change deductions may be, they will never match the inspired eyewitness record of God’s unique, stupendously powerful, all-encompassing, supernatural work of creation in the first week of the earth’s history, only about 6,000 or so years ago. And whatever we observe in the present world, including what’s in its rocks, when interpreted in the light of what God’s unchanging Word tells us, will always be consistent with that inspired, infallible historical record.