Late Mesoproterozoic magnetostratigraphic results from Siberia: Paleogeographic implications and magnetic field behavior

Global events across the Mesoproterozoic–Neoproterozoic boundary: C and Sr isotopic evidence from Siberia

“…Second, both the Malgina and Linok Formations demonstrate regionally persistent and similar polarity reversals. The lower parts of both units exhibit frequent alternation of normal and reversed polarity zones, and the upper parts demonstrate a gradual disappearance of normal zones, more evident in the Linok Formation; its upper part is almost completely dominated by reversed polarity (Gallet et al, 2000). Though available data are insufficient to provide a detailed correlation between the two regions, results are consistent with correlation between the Linok and Malgina Formations.…”

“…Micropaleontological studies indicate that the Totta and Bezymyannyi assemblages of organic-walled forms are nearly identical in composition (Pyatiletov, 1988;Veis, 1988;Hermann, 1990;Veis et al, 1998b). Furthermore, recent paleomagnetic data from the Uchur-Maya and Turukhansk regions (Pavlov and Petrov, 1996;Gallet et al, 2000) reveal two important features that suggest a close linkage between the Linok and Malgina Formations. First, the paleopole positions of the Linok and Malgina Formations are nearly identical, after correcting for relative motion within the Siberian craton during the Paleozoic opening of the Vilyui rift (Pavlov and Petrov, 1996;Smethurst et al, 1998).…”

“…3) were based on a striking coincidence in superposition of lithologies (Semikhatov and Serebryakov, 1983), on a compositional resemblance of successive stromatolite assemblages (Semikhatov, 1962;Semikhatov and Serebryakov, 1983;Semikhatov, 1991;Shenfil', 1991), on similarities in microfossil assemblages (German, 1981a,b;Pyatiletov, 1988;Veis, 1988;Jankauskas et al, 1989;Hermann, 1990;Veis et al, 1998aVeis et al, ,b, 1999, on paleomagnetic data (Pavlov and Petrov, 1996;Gallet et al, 2000) and on radiometric age data (see Semikhatov and Serebryakov (1983) and Shenfil' (1991) for bibliography and review).…”

Symmetry and stability of the geomagnetic field

“…On the other hand, a 50 m composite section of micritic limestone and shale of the Siberian Malgina Formation records 16 reversals from $1100-1050 Ma [Gallet et al, 2000]. These reversals are cleanly recorded, and the magnetization passes several stability tests.…”

“…Since then five detailed records between 1050 and 2775 Ma have become available [Strik et al, 2003;Halls, 1991;Elston et al, 2002;Gallet et al, 2000], which document around 45 reversals in time intervals totaling 225-250 Myr, an average reversal frequency of 0.2 Myr…”