Siluro‐Devonian paleomagnetic results from the Tuva Terrane (southern Siberia, Russia): implications for the paleogeography of Siberia

Abstract

New paleomagnetic data from seven sections of Siluro‐Devonian age sedimentary sequences in the Tuva Terrane (south Siberia, Russia) reveal the presence of up to three different components of magnetization. Component A is of recent or Late Mesozoic‐Cenozoic origin, and component B, identified unambiguously in 25 samples from one section, yields a sample mean direction (Declination/Inclination) of 300.6/−54.7 (k = 42.2, α95 = 4.5°) in geographic and 283.9/−63.5 (k = 45.4, α95 = 4.3°) in stratigraphic coordinates. However, since the results of the fold test are inconclusive, no further attempt has been made to assign an age to this magnetization. Component C, with unblocking temperatures of 500°–680°C, is identified in all seven sections and with dual polarity. After bedding correction, the section mean directions all plot along a common small circle in stereographic projection with a mean inclination of 42.1° (N = 7 sites, k = 184.2, α95 = 2.9°). It passes the inclination‐only fold test, the within‐site fold test (both on the 95% significance level) and the reversal test and is thus interpreted as being primary in origin and Siluro‐Devonian in age. Adopting the normal polarity option for component C yields a paleolatitude of 24°N (±2°) for the Tuva Terrane. On the basis of geological evidence, the Tuva Terrane was clearly accreted to Siberia by early Silurian times. The results obtained in this study, therefore, indicate lower paleolatitudes for Siberia than those predicted from previously published Apparent Polar Wander Paths for the Siberian Platform and demonstrate that Siberia was positioned between the equator and 30°N during latest Silurian/earliest Devonian times. These new results are also supported by paleoecological and paleoclimatological evidence. The dispersion of declinations along a small circle is indicative of clockwise block rotations within the Tuva Terrane of up to 72° with respect to Siberia.