GLOBAL OXYGEN MODELS: CONSTRAINTS FROM THE RECORD OF THE GLOBAL COAL AND OIL RESERVES AND THE EVOLUTION OF THE LARGER BENTHIC FORAMINIFERA

Oxygenic photosynthesis is the major significant source of free oxygen on Earth’s surface. It is linked generally to photosynthetic eucariots that are the major producers of the coal and oil reserves. The widely accepted model of atmospheric O₂ (Berner, 2006) suggests the maximum oxygen within the Pennsyllvanian-Cisuralian (Penn-Cis) time (around 300 Ma) with other smaller positive peaks at Silurian-Devonian transition, late Triassic and late Cretaceous-Neogen transition. The Jurassic-early Cretaceous (J-K1) time considered as the lowermost oxygen concentration in the Earth history. The Penn-Cis maximum linked to the massive coal burial in swamps during the late Paleozoic (360 to 270 million years ago), formation of vast coal deposits and to increased wildfires (Glasspool and Scott, 2010). An alternative model suggest much higher oxygen concentration during J-K time (Bergman et al., 2004), but it is not commonly accepted among the researchers. Coal and oil global reserves have two major peaks. One corresponds to Penn-Cis transition and consistent with both models. The other excessive coal and particularly oil reserves occur in J-K1 (Vyshemirskii and Kantorovich, 2001). During this time, the Berner model suggests global oxygen minima, whereas the Bergman model suggests an oxygen maximum even higher as the Penn-Cis one. Frequent wildfires also reported during J-K time (Belcher et al., 2008). The appearance first larger benthic foraminifera with symbionts linked to the high oxygen concentration in Penn-Cis (Payne et al., 2010). The second origination of larger benthic foraminifera appears during middle Jurrasic (Lituoloidea/Pfendorinoidea) and particularly in Cretaceous (symbiont-bearing Numulitids etc.) time that is consistent with the major global oil and coal reservoirs and frequent wildfires. It is well fits with the Bergman model, but contradicts with the Berner model. The widespread distribution of symbiont-bearing foraminifera during Cenozoic time (Rotalinids/Alevolinids/Soritids) suggests that the level of oxygen was close the same or even higher as in J-K time. This is again more consistent with the Bergman model. This study supported with NSF grants 014G106200 and 014G106225 and is also performed according to the Russian Government Program of Competitive Growth of Kazan Federal University.