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Bioelectromagnetism

FIGURE 6.11 Temporal evolution of reversal rate, O2 level, and marine diversity over the Phanerozoic (Wei

et al., 2014). Ca, Cambrian; O, Ordovician; S, Silurian; D, Devonian; C, Carboniferous; P, Permian; Tr, Triassic;

J, Jurassic; K, Cretaceous; Pg, Paleogene; Ng, Neogene. (a) GMF reversal rate. Te solid line is total reversals

within a 10 Myr bin (time period) from the new database (Ogg et al., 2008). Te dashed line is the relative rever­

sal rate to represent the trend of reversal rate from an older database (McElhinny, 1971). Te blocks show the

superchrons (Merrill and Mcfadden, 1999). KRS, Kiaman Reversed Superchron (~267–313 Ma); CNS, Cretaceous

Normal Superchron (~83–125 Ma); MRS, Mayero Reversed Superchron (~463–481 Ma). (b) Modeled percentage

and amount of atmospheric O2 over time (Berner, 2009). (c) Number of marine genera (Alroy, 2010). Te blocks

show the gradual pattern of fve well-known mass extinctions (the Ordovician–Silurian [O–S], the Late Devonian

[Late D], the Permian–Triassic [P–Tr], the Triassic–Jurassic [Tr–J], and the Cretaceous–Paleogene [K–Pg] extinc­

tions), and the sixth mass extinction (the Neogene [Ng] extinction) has not been confrmed. (Reproduced with

permission from Wei et al. (2014), Copyright 2014, Elsevier. It is licensed under the Creative Commons Attribution

3.0 International.)

Moreover, Wei et al. (2014) simulated the oxygen escape rate for the Triassic-Jurassic (Tr-J) extinction

event (the fourth mass extinction) using a modifed Martian ion escape model with an input of quiet

solar wind inferred from Sun-like stars. Te simulation predicted that GMF reversals could enhance

the oxygen escape rate by three to four orders only if the MF was extremely weak, even without consid­

eration of space weather efects (Wei et al., 2014). Consequently, it is estimated that the global hypoxia

might gradually kill numerous species (Wei et al., 2014).