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Bioelectromagnetism

FIGURE 6.8 Te Permian magnetostratigraphy and the Illawarra Reversal (Isozaki, 2009, modifed from

Gradstein et al., 2004). G–LB, Guadalupian–Lopingian boundary; P–TB, Permian–Triassic boundary. (Reproduced

with permission from Isozaki (2009), Copyright 2009, Elsevier.)

Te Kiaman Reverse Superchron ended ~50 million years (Myr) before the G–L boundary, and since

then it has suddenly changed to an era in which the polarity changes frequently. Tis change in the GMF

reversal pattern is called the “Illawarra Reversal” placed at 265 Ma around the Wordian–Capitanian

boundary in the Guadalupian (Isozaki, 2009).

Te Illawarra Reversal and the G–L boundary event record the signifcant transition processes from

the Paleozoic to Mesozoic–Modern world (Isozaki, 2009). One of the major global environmental

changes in the Phanerozoic occurred almost simultaneously in the latest Guadalupian, as recorded in (1)

mass extinction, (2) ocean redox change, (3) sharp isotopic excursions (C and Sr), (4) sea-level drop, and

(5) plume-related volcanism (Isozaki, 2009). Te Illawarra Reversal event records that a major modula­

tion has occurred in the process of the geodynamo mechanism. Te Illawarra Reversal represents the

most prominent marker in magnetostratigraphic correlation of the Late Paleozoic. Isozaki (2009) esti­

mated that this major change in the stability in the GMF refects a mode change in geodynamo in the